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OU 164150 


Call No. & fc> ^/^ S3 ^Accession No. 2 'i ^ V 
Author fYir-zrk'bni &-<- j A-*~t&* . / " . 


This book sno/Jld be returned on or before the date last marked below- 

by the same author: 

CHARACTERS (Annals of Botany, vol. 42} 

(TERTIARY POLLEN, II) (Bulletin of the Torrey 
Botanical Club, vol. 60} 


(The McGratv-Hill Co., New York and London) 


(Botanical Review, vol. 2} 

(Natural History, vol. 43} 

1942 ATMOSPHERIC POLLEN (in Aerobiology, 
A.A.A.S. Publication No. 17} 


edited by Frans Verdoorn 
Volume XV 




1 ne six illustrations ot pollen grains nere reproduced are trom one ot the beau- 
tiful hand-colored lithographic plates of KARL JULIUS FRITZSCHE'S immortal work, 
Ueber den Pollen, published at St. Petersburg in 1837. 

Figure one shows the grain of the common squash or field pumpkin (Cucurbita 
Pepo). The grain has absorbed moisture causing the protrusion of its contents as a 
papilla through one of its germ pores. Figure two shows a side view of a grain of 
"Astrapaea penduliflora," a member of the genus generally called in modern texts 
Assonia of the Sterculeaceae, and to which the Zulu cherry belongs. Figure three is 
of a grain of "Sida abutilon" of the Malvaceae. In the original plate it is colored a deep 
yellow due to its superficial coating of yellowish oil. Figure four is of the same grain 
as it appears when immersed in water and oriented so as to bring one of its germ pores 
uppermost. Figure five shows a sterile grain of the Chinese hibiscus {Hibiscus rosa- 
sinensis} . It is nearly colorless and transparent because, being sterile, it is quite empty. 
Figure six shows a grain of the common hollyhock ("Alcea rosea"). In the original 
plate this grain is shown a bright pink color with the spines a deep red. This is because 
it was treated with strong sulphuric acid which dissolves out the cell contents and 
changes the color at the exine from yellow to bright red. These two latter species 
belong to the Malvaceae as does Sida abutilon of which the pollen grain is shown in 
figures three and four. 

Though the work of FRITZSCHE was done more than a hundred years ago, his 
splendid plates have been seldom equalled in beauty, clarity and truthfulness. 


Their Appearance, Distribution, Time of 
flowering, and their Role in Hayfever, 
with special Reference to North America 



Associate Director of Research in Allergy > Lcderle Laboratories, 
Pearl River, N. Y. 


Published by the Chronica Botanica Company 

First published MGMXLV 

By the Ghronica Botanica Company 

of Waltham, Mass., U. S. A. 


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The study of hayjever jails into two fields the clinical and the 
botanical each so broad of scope and widely differing in character 
that for one to excel in one is almost to preclude the possibility of ex- 
celling in the other. The past twenty-five years approximately the 
time since pollen has been generally recognised as the cause of hay- 
fever has seen the accomplishment of much excellent work in both 
fields, but that of the former greatly exceeds that of the latter, and the 
facts of the latter field still remain scattered and so mingled with fan- 
cies that one who is not a trained botanist could scarcely be expected 
to separate them. This book is intended, therefore, to interpret the 
botanical facts of hay fever in terms of their clinical significance. 

Here are described all of the plants known to cause hayjever, most 
of those reasonably suspected of doing so, and many which have been 
mentioned in hayjever literature, possibly "wrongly. In the plant de- 
scriptions I have not attempted to define the species beyond pointing 
out a jew of the salient features which may readily be used and most 
easily retained in memory. 

The plants are presented in the sequence of ENGLER and PRANTL in 
their "Natiirliche Pflanzenfamilien". In the choice of botanical names 
usage and expediency have been my guides. Nor have I attempted to 
settle the questions of priority, nor even to make the names conform* 
either to the "International Rules of Botanical Nomenclature'^ or to 
the "American Code of Botanical Nomenclature". For the names of 
the grasses I have followed principally HITCHCOCK; for those of trees 
principally SARGENT ; for those of cultivated plants BAILEY ; and for 
those of the ragweeds and their relatives RYDBERG. Otherwise I have 
given primary choice to names of current usage especially in hayjever 
literature, except where these have appeared to be definitely wrong or 
misleading. Where more than one name is commonly used those of 
secondary choice are added as synonyms. 

For the capitalisation of specific names, since these are all Latin 
or at least Latinised in form, it seems that one has no choice but to 
follow the Latin rules for capitalisation. Consequently names of people 
and names of genera which are used as nouns, are always capitalised, 
while names of countries and places which are used as adjectives are 
not. Hence the capitalisation in such names a-s Populus Sargentii, Cy- 
nodon Dactylon, but lack of capitalisation in such as Artemisia cana- 
densis. English names are given as jar as these are known to the 

Roger P. Wodehouse viii Hayfever Plants 

author. In fact an attempt has been made to present all the vernacular 
names which have any use or value whatever, but some which are ob- 
vious translations of the Latin or otherwise useless have been rejected. 
Where more than one vernacular name is given, the name of preference 
is placed first. 

All of the illustrations are the work of the author, except where 
otherwise indicated. Those of plants were prepared from living or oc- 
casionally herbarium specimens especially for this volume. 

It is a pleasure to acknowledge my indebtedness and express sin- 
cerest appreciation of the generous help I have received from friends 
and colleagues. Especially am I indebted to Professor L. R. ABRAMS 
for reading the sections on the regional botany of the Southwest, and of 
southern California, and to Dr. JOHN H. BARN HART for help in solv- 
ing questions of nomenclature, and to Professor W. F. WELLS for the 
description and figure of the Wells Air Centrifuge, to Dr. RALPH 
Bo WEN for reading the manuscript, and to Professor G. ERDTMAN 
for the description and figure of the Aerosol Collector. I am also in- 
debted to the director and staff of the New York Botanical Garden, 
where much of the work was done, for the use of the herbarium and 
library and much incidental assistance. 


To win the secrets of a weed's plain heart. 


The thorns which I have reap'd are of the tree 
I planted ; they have torn me, and I bleed. 
I should have known what fruit 
would spring from such a seed. 


Upon the land of my people shall come up thorns and briers ; 
yea upon all the houses of joy in the joyous city. 

ISAIAH 32:13. 

Cursed is the ground for thy sake; in toil shalt thou eat of it all the days 

of thy life ; 
Thorns also and thistles shall it bring forth to thee; and thou shalt eat the 

herb of the field. 

Genesis 3 : 17, 18. 

Grass is the forgiveness of nature her constant benediction. Fields 
trampled with battle, saturated with blood, torn with the ruts of cannon, grow 
green again with grass, and carnage is forgotten. Streets abandoned by traffic 
become grass-grown like rural lanes, and are obliterated. Forests decay, har- 
vests perish, flowers vanish, but grass is immortal. Sown by the winds, propa- 
gated by the subtle horticulture of the elements, which are its ministers and 
servants, it softens the rude outline of the world. Its tenacious fibres hold the 
earth in its place, and prevent its soluble components from washing into the 
wasting sea. It invades the solitude of deserts, climbs the inaccessible slopes 
and forbidding pinnacles of mountains, modifies climates, and determines the 
history, character, and destiny of nations. Unobtrusive and patient, it has 
immortal vigor and aggression. Banished from the thoroughfare and the 
field, it abides its time to return, and when vigilance is relaxed, or the dy- 
nasty has perished, it silently resumes the throne from which it has been ex- 
pelled, but which it never abdicates. It yields no fruit in earth or air, and 
yet should its harvest fail for a single year, famine would depopulate the world. 


C U N T E N L S 

Chapter 1 



























Chapter 2 


Ginkgoaceae 20 

Coniferae 21 

Abietineae 21 

Pinus 21 

Picea 23 

Abies 25 

Tsuga 25 

Cupressineae 25 

Juniperus 26 

Chamaecyparis 28 

Hayfever Plants xi Contents 

Chapter 3 


Typhaceac 32 

Typha 32 

Arecaceae 34 

Gramineae 34 

Festuceae 38 

Bromus 38 

Festuca 39 

Poa 40 

Hordeae 44 

Agropyron 44 

Hordeum 45 

Lolium 45 

Aveneae 47 

Avena 47 

Agrostideae 48 

Chlorideae 51 

Bouteloua 53 

Phalarideae 55 

Zizaneae 55 

Paniceae 55 

Paspalum 56 

Andropogoneae 58 

Sorghum 58 

Tripsaceae 58 

Cypcraccae 59 

Car ex 59 

Juncaccae 60 


Salicaceae 61 

Salix 62 

Populus 64 

Betulaceae 67 

Betula 68 

Alnus 71 

Carpinus 72 

Ostrya 73 

Corylus 74 

Fagaceae 75 

Fagus 75 

Quercus 76 



Roger P. Wodehouse xii Hayfever Plants 





Casuarinaccac 81 

Juglandaccac 81 

Juglans 82 

Carya 84 


Myricaceae 86 

Myrica 86 

Ulmaceae 86 

Uhnus AND Plancra 87 

Celtis 89 

Moraceae OR Artocarpaceae 90 

Morns 90 

Cannabinaceae 91 

Polygonaceae 92 

Rumc.v 92 

Amaranthaceae 95 

Amaranthus 96 

Acnida 99 

Chenopodiaceae 100 

Chenopodimn 103 

Atriplex 104 

Rosaceae 109 

Platanaceae 110 

Mimosaceae Ill 

Acacia 113 

Prosopis 113 

Pabaceae 114 

Simarubaceae 115 

Tiliaceae 116 

Tilia 116 

Accraceae 116 

Acer 116 




Oleaccae 121 

Ligustrum 121 

Fraximis 123 

Plantaginaceae 125 

Plantago 125 

Compositae 127 



Hayfever Plants xiii Contents 

Heliantheae 131 

Ambrosieae 132 

Iva 133 

Oxytenia 135 

Cyclachaena 135 

Dicoria 137 

Ambrosia 137 

Franseria 145 

Xanthium 147 

Hymenoclca 149 

Helenieae 150 

Arctotidae 150 

Calenduleae 150 

Inuleae 150 

Astereae 150 

Vernonieae 151 

Eupatorieae 151 

Anthemidcae 151 

Artemisia 153 

THE vulgaris GROUP 155 

THE campestris GROUP 159 

Senccioncac 162 

Cynareae 162 

Mutisieae 162 

Cichorieae 163 

Chapter 4 




ELMS 166 





OAKS 167 








Roger P. Wodehouse xiv Hayfever Plants 





ELMS 173 



OAKS 173 






Juniperus 178 

Corylus 178 

Populus 178 

Betula 179 

Quercus 179 

Carya 179 

Tricholaena rosea 179 

Ligustrum 179 

Phleum AND Dactylis 1 79 

Amaranthus 179 

Acnida tamariscina 179 

Ambrosia 181 

Cyclachaena 181 

Xanthium 181 

Iva 181 

Artemisia 181 

Salsola 181 

Ulmus 182 

Sorghastrum nutans 182 

Baccharis halimijolia 182 

Broussonetia papyrijcra 182 

Casuarina 182 









Hayfever Plants xv Contents 

FUNGI 186 






ASH 189 

OAKS 190 












Kochia 192 

THE Ambrosieae 192 








Artemisia 195 

Atriplex 195 

Ambrosia pumila 195 

Franseria 195 

Hymenoclca Salsola 196 



Acacia 197 







OAKS 200 

Eucalyptus 200 

ASH 200 

ELMS 200 

Roger P. Wodehouse xvi Hayfever Plants 





DOCKS 201 









TREES 204 








WEEDS 206 





Acnida 207 






TREES 209 





ELMS 211 

ASHES 211 

OAKS 211 





Hayfever Plants xvii Contents 

WEEDS 212 




DOCKS 212 




HEMP 213 








FIG. 1, Ranunculus acris (Buttercup), flower 1 

FIG. 2, Cornus florlda (dogwood), flowers 3 

FIG. 3, Asclepias Cornuti (milkweed), flower and pollinia 4 

FIG. 4, Pollen shelter for exposing atmospheric pollen slides 8 

FIG. 5, Aerosol collector 10 

FIG. 6, Wells air centrifuge 11 

FIG. 7, Cones of conifers 22 

FIG. 8, Pollen grains of Picea (spruce), Ginkgo biloba, Juniper us 
(cedar), Tsitga (hemlock), Larix (larch), Pinus (pine), and Abies 

(fir) 24 

FIG. 9, Staminate cone of Juniperus 26 

FIG. 10, Lilium (lily) seedlings 30 

FIG. 11, Ambrosia (ragweed), seedlings 31 

FIG. 12, Examples of foliage leaves of monocotyledons and dicotyle- 
dons 31 

FIG. 13, Typha latifolia (cattail flag) 33 

FIG. 14, Pollen grains of Phleum (timothy), Secale (rye), Carex 

(sedge) and Typha (cattail) 35 

FIG. 15, Spikelet of Triticum (wheat) 36 

FIG. 16, Festuca elatior (meadow fescue), flowering stalk 39 

FIG. 17, Festuca rubra (red fescue), flowering stalks 40 

FIG. 18, Poa annua (low-spear or annual bluegrass) 41 

FIG. 19, Poa pratensis (June or Kentucky bluegrass) 42 

FIG. 20, Dactylis glomerata (orchard grass), flowering stalks 43 

FIG. 21, Lolium perenne (perennial ryegrass), flowering stalks 46 

FIG. 22, Holcus lanata (velvet grass), flowering stalks 47 

FIG. 23, Phleum pratense (timothy), flowering stalks 49 

FIG. 24, Agrostis alba (redtop), flowering stalks 50 

FIG. 25, Cynodon Dactylon (Bermuda grass) 52 

FIG. 26, Anthoxanthum odoratum (sweet vernalgrass) 54 

FIG. 27, Sorghum halepense (Johnson grass) 57 

FIG. 28, Salix purpurea (willow) flowers 63 

FIG. 29, Populus (poplar) and Salix (willow) leaves 65 

FIG. 30, Betula alba (white birch), flowers 68 

FIG. 31, Pollen grains of Juncus (rush), Salix (willow), Populus 
(poplar), Betula (birch), Alnus (alder), Carpinus (bluebeech), Os- 

trya (ironwood), Corylus (hazel) and Fagus (beech) 69 

FIG. 32, Alnus (alder) flowers 71 

FIG. 33, Carpinus caroliniana (American hornbeam), staminate and 

pistillate catkins 72 

FIG. 34, Ostrya viryiniana (hop-hornbeam) 73 

FIG. 35, Corylus (hazel) flowers 74 

FIG. 36, Qucrcus alba (white oak), flowering twig 76 

FIG. 37, Quercus (oak) leaves 78 

FIG. 38, Juglans nigra (black walnut), flowering twig 82 

Hayfever Plants xix Contents 

FIG. 39, Jitglans cinerca (butternut), flowering twig 83 

FIG. 40, Pollen grains of Qucrcus (oak), Juglans (walnut), Carya 

(hickory), Celtis (hackberry) and Ulmus (elm) 85 

FIG. 41, Ulmus amcricana (white elm), flowering twig 87 

FIG. 42, Ulmus fulva (slippery elm), flowering twig 88 

FIG. 43, Runic x Acetosclla (sorrel dock) 93 

FIG. 44, Rumex crispus (curly dock) 94 

FIG. 45, Pollen grains of Myrica Gale (sweet gale), Morns (mul- 
berry), Madura pomifcra (Osage orange), Cannabis (hemp), Brous- 
sonetia papyrijcra (paper mulberry), Rinnex (dock), Salsola (Rus- 
sian thistle), A triplex canes cens (wingscale), Sarcobatus vermicula- 
tus (greasewood), Amaranthus retro flcxus (pigweed) and Liquidam- 

bar styraciflua (sweet gum) 95 

FIG. 46, Amaranthus Palmeri (carelessweed) 97 

FIG. 47, Amaranthus retroftexus (pigweed) 98 

FIG. 48, Acnida tamariscina (western waterhemp) 99 

FIG. 49, Chenopodium ambrosioides (Mexican tea) 104 

FIG. 50, Atriplcx Wriyhtii (annual saltbush) 107 

FIG. 51, Pollen grains of Rosa (rose), Platanus (sycamore), Prosopis 
(mesquite), Acacia, Olea (olive), Fraxinus (ash), Acer (maple) 

and Plantago (plantain) 1 12 

FIG. 52, Acer rubrum (red maple), flowering twig and flower 118 

FIG. 53, Acer saccharum (sugar maple), flowering twig 119 

FIG. 54, Acer Negundo (boxelder), flowering twig 120 

FIG. 55, Ligustrum ovalifolium (privet), flowering twig and flower. . 122 

FIG. 56, Plantago lanceolata (English plantain), plant in flower 126 

FIG. 57, Composite flowers 128 

FTC;. 58, Pollen grains of Ailanthus (tree-of -heaven), l^araxacum 
(dandelion), Ambrosia (ragweed), Cyclachaena (prairie ragweed), 
Xanthium (cocklebur), Helianthus (sunflower), Solidago (golden- 
rod), Artemisia (sagebrush ) and Chrysanthemum 129 

FIG. 59, Iva (marshelder) flowers 133 

FIG. 60, Iva ciliata (rough marshelder) 134 

FIG. 61, Cyclachaena xanthifolia (prairie ragweed), plant 136 

FIG. 62, Ambrosia (ragweed), staminate flower heads and florets. . . . 137 

FIG. 63, Ambrosia (ragweed) seeds 138 

FIG. 64, Ambrosia elatior (short ragweed), flowering branch 140 

FIG. 65, Ambrosia trifida (tall ragweed), flowering branch 141 

FIG. 66, Ambrosia bidentata (southern ragweed) 143 

FIG. 67, Franseria tenuifolia (slender ragweed), part of a flowering 

plant 146 

FIG. 68, Xanthium (cocklebur), plant and seeds 148 

FIG. 69, Franseria acanthicarpa (bur ragweed) 149 

FIG. 70, Tanacetum (tansy) and Artemisia 152 

Fir,. 71, Artemisia calif ornica (coast sagebrush) 156 

FIG. 72, Artemisia campestris caudata (tall wormwood) 160 

FIG. 73, The ten hayfever regions 165 

Chapter I 

The Flower: The purpose for which all flowers are designed is that 
of securing transportation of their pollen from the flower or one plant to 
that of another of the same species. The two principal agencies by which 
this is accomplished are insects and wind. A few aquatic plants, like eel 
grass, are pollinated under water; a few, like tape grass (Vallisncria) and 
water grass (Elodea) are pollinated on the surface of the water; and a few 
are pollinated hy humming birds, snails and other agencies. But the ma- 
jority, certainly all those which concern us in hayfever studies, are pollinated 
either by insects or by wind or by both. 

In spite of the enormous variety of form of flowers they are all built on 
the same general plan. The same elements of construction are used in the 

FIG. 1. Buttercup (Ranunculus acris} flower, 
longitudinal section, diagrammatic to show the parts 
of a flower : An., Anther ; Fil., Filament ; Pi., 
Pistil ; Rec., Receptacle ; Pet., Petal ; Sep., Sepal. 

different forms in varying size, shape, color and arrangement, a circumstance 
which makes their understanding easy when once the plan is learned. The 
common buttercup (fig. 1) offers an example of a flower of which the 
elements of construction are relatively simple, representing a form from 
which the others may have been derived. If the flower is split in two ver- 
tically it will be seen that the top of the stem is carried well up into the 
flower ending in a dome-shaped expansion, the receptacle, upon which the 
parts of the flower are assembled. These are arranged in four series known 
as the calyx, corolla, stamens and pistils. The calyx or outer series consists 
of generally five greenish or colorless parts called individually sepals. These 
enclose the more vital parts in the bud, protecting them from injury until 
it opens. After which they are likely to fall away. So, unless the flower 
is observed in the bud or very young, the sepals may be missing. Within the 

Roger P. Wodehouse 2 Hayfever Plants 

calyx is found the corolla, consisting of the same number of parts as the 
calyx, generally five, which are called the petals. These are golden yellow 
in the buttercup and each is supplied with a nectariferous pit and scale at 
the base of the blade. The calyx and corolla together are called the perianth 
because they are arranged around the flower. Inside of the corolla are the 
stamens, variable in number. Each consists of a short stalk, the filament, 
curving upward and outward and bearing at its tip a two-lobed sac, the 
anther, in which the pollen is borne. Each lobe of the anther bears a longi- 
tudinal groove along which it may split open in due time, and if the flower 
is about to shed its pollen a moderately strong lens will reveal the grains 
starting out from the clefts. Above the stamens the receptacle is abruptly 
narrowed and extended upward to a point bearing the pistils, in this case 
also called the carpels, each consisting of a swollen base known as the ovary 
since it contains the ovule, and a short outwardly curving projection known 
as the style of which the upper side, which is called the stigma, is sticky and 
specially designed to catch the pollen grains and provide them with the 
proper conditions of moisture and nutriment to stimulate their germination 
and sustain their growth. 

The essential parts of the flower are the stamens and pistils, for they 
alone produce the pollen and ovules which perform the necessary functions 
of the flower. In some plants either the calyx or corolla, or both, may be 
absent but still the flower is regarded as perfect. In others some of the 
flowers have only stamens and some only pistils. Such flowers are imper- 
fect, and if the staminate and pistillate flowers are both on the same plant, 
they are called monoecious, and if on different plants, dioecious. Flowers 
with such extreme modifications are common among hayfever plants. For 
example, the ragweeds and cockleburs are monoecious, with the staminate 
flowers arranged in spikes at the ends of the branches and the pistillate just 

Entomophilous Flowers : Insect pollinated or entomophilous flow- 
ers generally have some obvious method of attracting insects, by scent which 
may be either pleasant or unpleasant to our senses, or by bright and con- 
spicuous colors, which are generally exhibited by the corolla as in the butter- 
cup and lily, by the calyx as in the hepatica and anemone, by the stamens 
as in Callistemon and Acacia, by transformed leaf bracts as in the dogwood 
(fig. 2) and poinsettia, or by the whole inflorescence as in the cockscomb 
and globe amaranth. They generally produce nectar which serves to en- 
courage the visits of insects, though many flowers are visited solely for their 
edible pollen, and others, taking advantage of the insects' gullibility and 
uncontrolled sex reflexes, are merely a snare and delusion, offering the 
insect nothing for his visit ; some of the orchids are like this. The stamens 
of entomophilous flowers are generally protected by the floral parts so that 
the pollen can not be easily reached except by an appropriate insect, and 
the pollen is usually sticky and not easily blown away by the wind. In 
general the more perfect the adaptation to insect pollination the smaller the 
amount of pollen produced, for the flower is primarily a device for securing 
pollination with the minimum expenditure of pollen. 

Chapter I 


The Botany 

By this criterion the orchids rank highest among the flowering plants. 
Their pollen is produced in masses, the grains united in fours and these in 
turn bound tightly together by webby filaments. The pollen masses are 
often provided with a sticky disk by which they become cemented to the 
head or proboscis of a visiting insect. They become so firmly attached to 
the body of the insect that he is often quite unable to detach them, except 
by visiting another flower when they stick to the stigma. Such pollen can 
not possibly cause hay fever. 

FIG. 2. Dogwood (Cornus florida} flowers, an 
example of entomophily with showy bracts. 

Another example of highly perfected insect pollination is found in the 
milkweeds (fig. 3). Here again the pollen grains are all united into com- 
pact masses and so fixed in the anthers that they can not be removed except 
by an excited insect letting his foot slip into one of the tiny clefts of the 
flower, when the pollen mass clamps firmly onto his foot and can only be 
removed by bringing the pollen mass in contact with the stigma of the next 
flower he visits. Such pollen is totally incapable of causing hayfever. 

In the sweet peas, clovers, vetches and related plants the stamens are 
tightly enclosed in the lower petal so that it is only when visited by an insect 
heavy enough to pull the petal down that the pollen is exposed ; then it 
sticks to the insect's thorax and is carried away. Sometimes the pollen is 

Roger P. Wodehouse 


Hayfever Plants 

hidden in the tube of the corolla where it can not be removed except by an 
insect probing into the flower in search of nectar. All such highly specialized 
flowers can be totally disregarded as causes of hayfever. Their pollen is 
so closely guarded that it can not escape. 

FIG. 3. Milkweed (Asclcpias Cornuti), an ex- 
ample of a flower highly specialized in entomo- 
phily ; A, a single flower ; B, pollinia greatly en- 

Imperfectly Entomophilous Flowers : But entomophilous flowers 
are not always so perfectly adapted to pollination by insects. For example 
some kinds of goldenrod, sunflowers and dahlias are rather loose with their 
pollen. Often it may be found scattered on the leaves of the plants, or, if 
the plants are put in water in the house, it becomes scattered on the table 
where they are standing. If the bees do not carry off this pollen it may 
easily be blown away and become to some degree atmospheric. At any rate 
the pollen of sunflower and goldenrod is often caught on atmospheric pollen 
slides, though always in very much smaller quantities than that of the rag- 
weeds and grasses. Consequently such imperfectly insect-pollinated plants 
as the sunflower, goldenrod and dahlia must be given some consideration 
in hayfever studies. But they should not be taken too seriously. 

Amphiphilous Flowers : Still other plants are both wind and insect 
pollinated. An outstanding example of this class is the willow (fig. 28). 
Its flowers are bright yellow in color, sweet scented and abundantly supplied 
with nectar which is greedily sought by bees in the early spring when other 
flowers are scarce. By these tokens it must be regarded as insect pollinated. 
But if we examine the flowers closely they are found to be extremely simple. 
They are aggregated in spikes or catkins with the sexes entirely separate. 
The male flower is without calyx or corolla, consisting of just two stamens, 

Chapter I 5 The Botany 

each in the axil of its bract with a glandular scale at its base. They produce 
a large amount of pollen which is only slightly sticky and floats away in the 
air when not carried off by insects, and may even at times cause hayfever, 
so by these tokens willow flowers are wind pollinated. If one method fails 
them they can fall back on the other. 

Anemophilous Flowers : Pollination by wind is the most ancient 
and primitive method. It is scarcely different from the anemophilous dis- 
semination of spores by the ferns and fungi. It appears to have been the 
only method employed by the ancient gymnosperms, the Cycadofilicales, 
Bennettitales and Cordaitales, mighty races of trees of past geological ages. 
It is likewise the method of pollination among the living gymnosperms, such 
as the conifers. In fact the pines, firs, hemlocks and spruces are the great- 
est living practitioners of anemophily, if the amount of pollen produced is 
to be taken as the criterion. So much pollen is given off by these that it is 
sometimes to be seen floating like a cloud above the forests. It accumulates 
on the surfaces of lakes and ponds in such quantities that it may be scooped 
up by the pound. Sometimes it is washed out of the forest by heavy rains 
and spread over the ground giving rise to the so-called "sulphur showers". 

Among the flowering plants (angiosperms) anemophilous flowers are 
also characterized by simplicity of structure, but this is a simplicity of reduc- 
tion and not of primitiveness. They are not showy, do not produce nectar, 
are not scented and are of little or no interest to insects. They may produce 
enormously more pollen than their insect pollinated relatives though they 
do not always and this is dry and powdery. There is a marked tendency 
toward the separation of sexes, and for the flowers to appear early in spring, 
particularly among trees and shrubs, before the leaves are fully developed. 

One of the most interesting things about anemophily is that it occurs 
in many families which are entirely unrelated, showing that it is a recent 
evolutionary development. It is found in the grass family ; all of these are 
wind pollinated, except a few like the cultivated oat and some varieties of 
wheat, which are self-pollinated. It also characterizes all of the goosefoot 
family, most of the pigweed family, the plantains, and a few genera like the 
docks in the buckwheat family, the ragweeds and mugworts in the composite 
family, and many others. 

What Makes Some Plants Cause Hayfever? In order to cause 
hayfever pollen must have certain characteristics which may be summed up 
as buoyancy, abundance and allergenic toxicity. To judge if a plant is likely 
to cause hayfever one must discover by observation or experiment its mode 
of pollination. If it is entirely entomophilous it should be unconditionally 
excluded. There is no use in considering such plants as orchids, snap- 
dragons, milkweeds, lupins and the many showy garden and wild flowers 
which are often suspected by the uninitiated. If the plant is loosely ento- 
mophilous or amphiphilous it may be suspected, especially if it belongs to 
one of the hayfever-plant families. Goldenrod, sunflower, chrysanthemum 
and stevia, for instance, belong to the composite family, the same family as 
the ragweeds, and they can on occasion cause hayfever. Privet and olive 

Roger P. Wodehouse 6 Hayfever Plants 

belong in the same family as the ashes, and both occasionally cause hayfever. 
But it is only among the truly anemophilous plants that one need look for 
the really important causes of hayfever. And by no means all of these are 
important for anemophily only conditions one of the necessary attributes, 
that of buoyant pollen. It is frequently stated that wind pollinated plants 
are characterized by their production of excessive quantities of pollen. This 
is true of only relatively few; indeed the work of POHL (1937) shows that 
there is really no relation between the mode of pollination and the amount 
of pollen produced. Most anemophilous plants shed far too little pollen, or 
else the plants themselves are too scarce, to be of any consequence in hay- 
fever. There are about 1100 species of grass growing naturally in the United 
States, for example, most of them wind pollinated, yet 35 would be a gen- 
erous estimate of those which have anything to do with hayfever, and those 
which are its important causes number about seven. The others either shed 
too little pollen or are themselves not abundant enough. 

Hayfever Toxicity: Equally important is the allergenic toxicity of 
the pollen. The only way to settle with certainty the question of this is by 
actual clinical test with pollen-sensitive individuals. Fortunately, however, 
allergenic toxicity is found to be rather strictly a family character, limited to 
relatively few families. The most important of these are : 

Gramme ae, the grasses. 

Compositae, ragweeds, mugworts, goldenrods, etc. 
Chenopodiaceae, Russian thistle, saltbushes and chenopods. 
Amaranthaceae, pigweeds and waterhemps. 
Plantaginaceae, plantain. 
Polygonaceae, dock and rhubarb. 


Betulaceae, birches, alder and hazel. 
Fagaceae, beeches, oaks and chestnut. 
Ulmaceae, elms and hackberry. 
Moraceae, mulberries and paper mulberry. 
Juglandaceae, walnuts and hickories. 
Salicaccae, poplars and willows. 
Aceraceae, maples. 
Oleaceae, ashes, olive and privet 

The pollen of the grass family possesses hayfever toxicity to rather high 
degree, and so universally throughout the family that some authorities 
maintain that the pollen of one grass generally they use timothy is suffi- 
cient to treat sensitization to all grasses. The pollen of the composite family 
possesses allergenic toxicity to an even higher degree, and it appears to be 
universal in the family so that the relative importance of the various species 
in hayfever is almost entirely a matter of the buoyancy and abundance of 
their pollen in the air. 

Other families which possess this kind of toxicity are the Chenopodia- 
ceae, with Russian thistle and the saltbushes as examples, the Amarantha- 
ceae with the pigweeds and water hemps, the Plantaginaceae with English 
plantain apparently the only species which can qualify on other counts, and 

Chapter I 7 The Botany 

the Polygonaceae possess it to only a slight degree as exemplified by the 
docks. On the other hand hayfever toxicity is largely lacking in other 
families which would otherwise qualify as hayfever plants. For example 
the cattails, the rushes and sedges are nearly or quite harmless in hayfever 
though the plants may be abundant and are often extravagant producers of 
buoyant pollen. Among the conifers which are mostly prolific shedders of 
buoyant pollen, only the junipers and their closest relatives, members of the 
Cypress tribe, have been shown to possess allergenic toxicity in sufficient 
degree to cause hayfever. It is probable, however, that in the phylogenic 
classification of the conifers if the same principles of classification had been 
followed as is used among the angiosperms the tribe of the junipers and 
their allies would have been given the rank of a separate family. At any 
rate, admitting this exception, hayfever toxicity appears to be a family 
character. Generally speaking, from a hayfever standpoint, first considera- 
tion should be given to those plants which belong to families in which occur 
known causes of hayfever. 

Regional Surveys : In every region where hayfever occurs it is essen- 
tial to the physician to know which plants are producing the pollen and 
exactly when each flowers and how much of each of the different kinds of 
pollen there is in the air. 

There are three sources from which this information is obtained, field, 
laboratory and clinical. They are supplementary to each other in such a 
way that a complete picture of the pollen situation can only be gained by a 
combination of all three. For the field study the area in question is divided 
into sections. Or representative sections are chosen of convenient size. 
These are visited at frequent intervals throughout the hayfever season. All 
anemophilous plants, and others which by unusual abundance or other 
characteristics should be suspected, are counted, their time of flowering 
noted, the relative amounts of pollen shed by each determined and samples 
of it collected. Methods of collecting and preserving pollen have been 
repeatedly described (KELLY 1928, WODEHOUSE 1935) so need not be dwelt 
on here. Suffice it to say that almost any flowers which are capable of 
causing hayfever will shed their pollen if cut and placed in water. If any 
plants are encountered which can not be identified with certainty, specimens 
should be dried and sent to a local botanist or to one of the large herbaria. 
Botanists are usually glad to make identifications providing complete speci- 
mens are sent. Small herbaceous species should include root, stem, leaves, 
flowers and, if possible, fruit. Trees and shrubs should include twigs, 
flowers and leaves, and a note regarding the missing parts, such as "tall 
tree with dark grooved bark", or "spreading shrub with light gray bark". 
And always the date, exact locality of collection and name of the collector 
should accompany each specimen. In case the plant is monoecious or dioe- 
cious both staminate and pistillate flowers should be included. Most botan- 
ists feel themselves more than compensated for making the identification if 
given a complete and properly dried specimen with the necessary record for 
their herbarium (see p. 15). 

Roger P. Wodehouse 8 Hayfever Plants 

Atmospheric Pollen : While the field observations are being carried 
on atmospheric pollen counts should be made every day to discover which 
kinds of pollen are in the air, and their abundance. This is the laboratory 
part of the problem. There are several methods of obtaining pollen counts, 
but the one generally employed is that of simply exposing microscope slides 
coated with some adhesive, the adhesive used depending upon the circum- 
stances. Unless the season is rainy or the atmosphere extremely damp, 
glycerine jelly is the adhesive of choice. 

In order to prepare the slides ordinary commercial glycerine jelly to which a small 
amount of a dye such as basic fuchsin has been added, is melted on a water bath, kept 
at a temperature below boiling point. The slide to be coated is warmed, clamped to 
the revolving disk of a slide turntable and spun as in ringing slide mounts. A small 
camel-hair brush is dipped into the melted jelly and stroked slowly from the center of 
the spinning slide outward to the ring marked on the turntable which corresponds to 
the size of the cover glass to be used in finishing the preparation. The whole process 

FIG. 4. Pollen shelter for exposing atmospheric pollen slides. 

takes only a few seconds, and enough slides to last a month can be made up at one 
time. Great care must be taken not to expose the slides to any dust during their 
preparation and storage lest they should become contaminated with extraneous pollen 
before they are used. 

For exposure the slide must be fastened securely, placed in an exposed 
situation and protected from rain. Various kinds of shelter have been 
devised for this purpose. That used by the author is shown in fig. 4. It 
consists of a copper can about 10 X 10 X 14 in. lying on its side. The top 
and bottom have been removed and inside the can, on its lower side, is 
fastened a heavy block of wood. To this is attached a smaller block to 
which is fastened a spring clothespin to hold the slide by one end, and a 
piece of cork upon which the free end of the slide may rest. The whole 
apparatus is nailed to a stout board which may be weighted or fastened to 
the roof of the laboratory or other support. 

After the slide has been exposed for 24 hours it is brought in, grains of 
sand or other materials which might prevent the cover from settling into 

Chapter I 9 The Botany 

place, are removed. The slide is then heated gently and a No. cover glass 
put over and lightly pressed into place. 

Vaseline Method: In case the atmosphere is moist or showers are 
frequent and likely to spoil the gelatine coating of the slide, vaseline may be 
substituted for the jelly. To do this a small spot in the center of the slide 
is smeared very lightly with clean vaseline. After the slide has been exposed 
as above and any extraneous material, if present, removed, a small fraction 
of a drop of melted stained glycerine jelly or lactophenol* is added and the 
cover pressed firmly into place. 

An interesting modification of this method is that used by REMPE (1937) 
in his remarkable studies on the dispersal of pollen by means of air currents. 
He used small brass tubes, 14 X 45 mm, with their ends wrapped with 
cellophane which was coated with vaseline. These he exposed by hanging 
in the crowns of trees or from the tops of tall poles. After exposure the 
cellophane was removed and pressed face down on a microscope slide for 

Open Dish Method: A method described by LUDI and VARESCHI 
(1936) is to expose without cover or protection of any kind a shallow dish 
such as a petri dish but deep enough to avoid being overflowed by rain. 
The bottom of the dish is covered with a thin layer of glycerine and water. 
After exposure the pollen, glycerine and accumulated rain water are washed 
out with pure water and centrifuged so as to concentrate all solid material 
into one or two cubic centimeters of liquid. Then this is boiled in 10 per cent 
potassium hydrate for three to five minutes to remove the cell contents of 
the pollen grains. The material may then be suspended in a measured 
volume of water and the pollen grains of a known fraction counted. From 
this may be calculated the number of grains falling into the dish per unit area. 

Erdtman Air Filtration Method: Professor G. ERDTMAN of the 
University of Stockholm has devised a method for filtering pollen and spores 
out of the air and at the same time metering the air. The apparatus (fig. 5) , 
which he calls the Aerosol Collector, is a small vacuum cleaner with its 
filter bag replaced by a plaited filter paper supported on an aluminum 
frame. All the air which enters is forced through the filter paper, and 
as it leaves the apparatus is led through a pipe where it is metered. 
Through one side of the exhaust pipe is inserted a pitot tube, a small tube 
with a short right-angled bend turned so that its orifice faces against the 
flow of air. The pressure exerted in the pitot tube by the flowing air is 
transmitted by a small rubber tube to a mercury manometer. The manome- 
ter is calibrated with the assistance of an ordinary air meter so that the 
pressure is read in terms of cubic meters of air flowing per hour. If the 
manometer is read at the start and finish of a run the total amount of air 
that passed through the apparatus can easily be calculated. At the end of 

* Phenol, 2 cc. Lactic acid, 2 cc. Glycerine, 4 cc. Water, 2 cc. (LEE, A. B. 

Roger P. Wodehouse 


Hayfever Plants 

the run the filter paper is removed from the apparatus and taken to the 
laboratory for analysis. 

The paper with its collected spores and pollen grains is treated with 
acetic anhydride and sulphuric acid, 9:1, heating to boiling on a water bath, 
to dissolve the filter paper and other unwanted organic material. The mix- 
ture is then centrifuged, the sediment washed to free it of the reagents, and 
suspended in a measured volume of water. A sample of this is removed by 
a pipette and placed in a specially devised counting chamber (ERDTMAN 
1935) similar to that used for counting bacteria but modified to adapt it to 
the much larger pollen grains. The counting chamber enables one to learn 
the number of grains of each species of pollen per cubic centimeter of the 

FIG. 5. Aerosol collector, after G. ERDTMAN. 

pollen suspension. From this can readily be calculated the number of grains 
per cubic meter of air which passed through the Aerosol Collector during 
the run. 

The Wells Air Centrifuge* : The Wells Air Centrifuge for Direct 
Microscopic Examination of Air (fig. 6) consists essentially of two concave 
discs face to face and spaced apart at their edges by the thickness of a cover 
glass. Through this marginal slit at the edge of the lens-shaped cavity, air 
is projected by the rapid whirling of the disc directly onto a celluloid foil 
which is supported in a metal collar surrounding the slit. The head formed 
by these two discs revolves at about 15,000 revolutions per minute, and the 
air is drawn into the concavity through an opening at the center of the 

* Contributed by WM. FIRTH WELLS, University of Pennsylvania. 

Chapter I 


The Botany 

upper disc and thrown out through the annular slit at the rate of about 3 
cubic feet per minute. The impinging velocity resulting from the enormous 
centrifugal force developed causes particles within the air to be deposited 
upon the film in a ridge at the angle where the air changes its direction 
sharply toward the outflow. 

The lower of the discs is attached by a flexible rubber sleeve to the shaft 
of the motor, and the upper to the collar in which the celluloid is placed 
and from which it can readily be removed. The insertion and removal of 
the celluloid strip is thus facilitated, after which it can be cut and fixed to 
a glass slide for direct examination, or otherwise manipulated if further 
treatment of the deposit is desired. 

Sampling then reduces to insertion of the celluloid strip and spinning 
the centrifuge for a period depending upon the volume of air it is desired 
to sample. A cubic meter of air is sampled in approximately ten minutes. 

Counting is simplified if the ridge of deposit is mounted parallel to the 
edge of the slide or is in the direction of motion of a mechanical stage. A 
low power objective is brought over the densest part of the ridge at one 

F IG< 6. Wells air centrifuge, after W. F. WELLS. 

end and the slide is made to traverse the length of the ridge under the eye 
of the person counting. One additional traverse above and one below the 
central traverse should include most of the particles, but if more than 10 
per cent of the count of the central traverse is obtained in either lateral 
traverse, another traverse should be made further from the center. 

The entire machine is contained in a small portable box, the complete 
weight of which is about ten pounds. The model illustrated is equipped 
with a universal motor, but it is possible to replace it with one running on 
storage battery current. The essential part of the machine being the spe- 
cially designed head, other adaptations may be devised if only provision is 
made for rapid revolution of the head with access to the air to be sampled. 

Film, obtained from the Celluloid Company, Newark, New Jersey, and 
cut into J4 -inch strips with an ordinary photographic trimmer has been 
entirely satisfactory. 

Roger P. Wodehouse 12 Hay fever Plants 

Gravity Methods : None of the gravity methods gives a reliable 
index to the absolute amount of pollen in the air, though it seems that they 
could be correlated with the Erdtman filtration or some other absolutely 
volumetric method. However, the number of grains per unit area falling on 
the slide or surface of liquid can be assumed to depend upon two factors, 
the abundance of the pollen grains in the air and their rate of fall. Upon this 
basis SCHEPPEGRELL (1922) has worked out a formula which was supposed 
to show the relation between the number of grains falling on a unit area in 
a given time and the number suspended per unit volume of air which is : 

7 X N 

n = 

v X t 

where n equals the number of grains per cubic yard, N the total number 
falling on one square centimeter, t the number of hours exposure, and v 
the velocity of fall in feet per second. The velocity of fall (v) SCHEPPE- 
GRELL stated he calculated from the formula, 

2g r* 

v = (Stake's law), 


where v equals the velocity of fall in cm per second, g the acceleration of 
gravity, r the radius of a falling sphere, and k the coefficient of viscosity of 
air. The velocities of fall thus calculated for pollen grains of all sizes he 
furnished in a table. Even if SCHEPPEGRELL had made his calculations 
correctly it is doubtful if they would have more than theoretical interest 
for they take no account of the shapes of the grains, which in their dry 
condition are hardly ever spherical, nor of their sculpturing. Nor do they 
take account of such variables as the specific gravity of the grains, the tem- 
perature and humidity of the air, and the velocity of the wind and direction 
in which it impinges on the slide slides placed vertically in the air current 
often catch more pollen than those placed horizontally. However, much 
more serious than these omissions was an unfortunate error which SCHEPPE- 
GRELL made in applying the formula of Stoke's law. In making his calcu- 
lations he used the measurements of the diameters of the pollen grains in- 
stead of their radii. Since these are squared his mistake introduced a rela- 
tively huge error, rendering all of his table useless. This error of SCHEPPE- 
GRELL'S has had a far-reaching and damaging effect on succeeding investi- 
gations, for it became the custom of some of the most productive investi- 
gators in the study of atmospheric pollen to report their results in terms of 
pollen grains per cubic yard, accepting without question SCHEPPEGRELL'S 
formulae so that their records are more misleading than useful. 

Attention was first drawn to SCHEPPEGRELL'S error by COCKE (1937). 
Applying the correction, he furnished a table, which he recommends to be 
accepted as standard form, part of which is as follows : 

Chapter I 13 The Botany 

Velocities of fall and formulae for computing concentration per cubic yard from 
the number (N) of smooth pollen per square centimeter on slides exposed for 24 



10 0.01 n = 29.1 N 

12 0.014 n = 20.8 N 

14 0.02 n = 16.6 N 

16 0.026 n = 11.2 N 

18 0.03 n = 9.7 N 

20 0.04 n = 7.3 N 

22 0.049 n = 5.9 N 

24 0.058 n = 5.0 N 

26 0.068 n = 4.3 N 

28 0.079 n = 3.7 N 

30 0.09 n = 3.2 N 

32 0.10 n = 2.9 N 

34 0.11 n = 2.7 N 

36 0.13 n = 2.2 N 

38 0.15 n = 1.9 N 

40 0.16 n = 1.8 N 
Reproduced from COCKE (1937). 

In discussing the importance of applying the correction COCKE points out 
that FEINBERG and STEINBERG (1933), in correlating their pollen counts 
with hayfever symptoms by applying SCIIEPPEGRELL'S formula, found that 
their pollen counts indicated that 25 grains of ragweed pollen per cubic yard 
was sufficient to produce symptoms, or 500 inhaled per day. Whereas, 
correcting for SCHEPPEGRELL/S error and allowing for the spicules on the 
ragweed pollen grains, the actual number indicated by the count was 196 
per cubic yard or 3920 inhaled per day. 

In a later publication COCKE (1938a) put his theoretical calculations to 
the test by an ingenious device which recorded all the pollen in metered air. 
He found remarkably close agreement between the measured and calculated 
values for pollen grains which are approximately spherical when dry. Rag- 
weed pollen he found to be under represented on the slides by 32.2 per cent 
and pine by 56.2 per cent. In the former the spicules, in the latter the blad- 
ders slow up their rate of fall by those amounts. In this paper the author 
furnishes a table which greatly facilitates the conversion of the number of 
grains caught into the number present per cubic yard of air, a part of which 
is reproduced here : 

Table for determining the number of pollen grains of a given size per cubic yard 

of air from the number of grains caught on one square centimeter in twenty-four 

18/i 20/A 22/x 24/t 26/x 28/t 30/t 32/t 34/* 36/i 38/i 40/x 

1 10 765 4433 3222 

2 19 15 12 10 9766 5444 

3 29 22 18 15 13 11 10 9 8765 

4 38 29 23 20 17 15 13 12 11 9 8 7 

5 48 37 29 25 21 18 16 14 13 11 10 9 

6 58 43 35 30 26 22 19 17 16 13 11 11 

7 68 51 41 35 30 26 22 20 19 15 13 13 

8 78 58 47 40 34 30 26 23 21 18 15 14 

9 87 66 53 45 39 33 29 26 24 20 17 16 
10 97 73 59 50 43 37 32 30 27 22 19 18 

Reproduced from COCKE (1938a) 

Roger P. Wodehouse 14 Hay fever Plants 

The method of using the table is simple. For example, if one catches 
ten grains of ragweed pollen in 24 hours, the grains are 20//, in diameter 
so he reads 73 in the vertical column but ragweed is slowed 32.2 per cent 
in its rate of fall by its spicules so he would add about one third of this 
number which gives a concentration of 97.3 per cubic yard. Of course for 
larger numbers, multiples of those shown in the first column may be used. 

The methods of recording pollen in general use give the grains caught 
per unit time, generally 24 hours, and do not tell much about the fluctuations 
of pollen density which may take place from hour to hour during the day. 
Recently HA WES, SMALL and MILLER (1942) have devised an apparatus 
with a clock-work mechanism which moves a slide across a jet of meter ed 
air which impinges upon it through a slit. In 24 hours' operation it dis- 
tributes the pollen from about five cubic yards of air along a band one cm 
wide and 6 cm long, so that the fluctuations in pollen density are continu- 
ously recorded. 

The techniques for appraising airborne populations of microorganisms, 
pollen and insects have been reviewed up to 1941 by the Committee on 
Apparatus in Aerobiology of the National Research Council (ANNAND 
et al. 1941). Other methods and apparatus, particularly those for use in 
aeroplanes, will be found in their report. 

Identification : By whatever method the atmospheric pollen is caught 
it must be accurately identified. Some help in this may be had from the 
author's book, Pollen Grains (WODEHOUSE 1935) in which the grains of 
many species are described and illustrated, also from Atmospheric Pollen 
( WODEHOUSE 1942&) which is an atlas containing descriptions and figures 
of all atmospheric pollen known to the author. But final identification is 
best made by actual comparison with known material. For this purpose 
a reference collection of mounted specimens of pollen is necessary. The 
collection should include specimens of pollen from all anemophilous and 
as many as possible of the common entomophilous plants of the region under 

Preparation of Pollen Slides : In order to prepare pollen for micro- 
scopic examination a small amount of dried pollen, about as much as 
can be picked up on the small end of a flat toothpick, is placed on the 
center of a microscope slide, and a drop of 95 per cent alcohol added. 
The pollen is then stirred with the toothpick and the alcohol drawn off with 
a tuft of twisted cotton to remove the oil. If there is much oil on the pollen 
a second or third application of alcohol is necessary. After all free alcohol 
has been drawn off, but while the pollen is still moist with it, a very small 
drop of melted glycerine jelly containing basic fuchsin is added and, keeping 
the slide warm by passing it several times quickly through a small flame, 
the pollen is stirred in with the toothpick until it is evenly distributed. Then 
a No. cover glass is warmed by passing it several times through the flame, 
while held vertically with the forceps, and pressed lightly onto the prepara- 
tion. It is of the utmost importance that the preparation be as thin as 
possible ; if the correct amount of jelly has been used it will just reach the 

Chapter I 15 The Botany 

periphery of the cover glass as the latter begins to press the pollen grains 
against the slide, so that the thickness of the mount is no greater than the 
diameter of the pollen grains. Slides prepared in this way can be studied 
with the most powerful oil-immersion lenses, which is essential to reveal 
their textures and fine sculpturing, and such slides will keep several years, 
though they are not actually permanent. 

If naturally shed pollen is not available suitable material can generally 
be obtained from good herbarium specimens. To do this a few mature 
anthers are removed with forceps under a hand lens, placed on a microscope 
slide and extracted with alcohol as before. Then a large drop of water is 
added, and brought to a boil by passing the slide several times through the 
flame. The anthers are then opened with needles under a dissecting micro- 
scope and the pollen scraped out. The empty anthers are removed, the 
water drawn off with a twisted tuft of cotton, a drop of melted basic-fuchsin- 
glycerine- jelly added and the preparation covered as before. This method is 
more troublesome than that with naturally shed pollen, but it gives equally 
good results and possesses a worthwhile advantage in that the pollen prepa- 
rations may at any time be referred to the exact specimens from which they 
came, in case the question of identification should arise. For this reason 
the slide should always be given a number corresponding to that of its 
herbarium specimen. 

Methods of collecting and preserving herbarium specimens are to be 
found in many botanical textbooks (e.g., BAILEY 1924, SWINGLE 1934) so 
need not be described here. Suffice it to say that specimens to be used for 
pollen preparations should be dried rapidly and completely, and in mounting 
they should be strapped, not glued, to the sheets, or a few extra flowers for 
dissection may be dried separately and enclosed in little paper packets glued 
to the specimen sheet. 

In the identification of atmospheric pollen it is rarely possible to tell 
the exact species, but it is generally possible to tell the genus and nearly 
always the family, and the species can be judged with only a small margin 
of doubt, by a knowledge of which plants are flowering at the time when 
the pollen is caught. For example the pollen grains of the grasses are all 
much alike, except for differences in size, yet if grass pollen is caught on 
the slides, let us say when sweet vernal-grass is in flower, and the grains 
which are caught correspond in size to those of sweet vernal-grass, it is 
reasonably certain that they are of that species. In this way the laboratory 
and field observations supplement each other. 

In general it is found that the symptoms of hayfever sufferers correspond 
in their appearance and severity with the incidence of the pollen of one or 
more species of plants in the region (SACK and GOLAN 1942). If pollen 
samples of these are tested by means of the skin test, their importance or its 
lack can be ascertained with certainty. 

Botanical Literature : The botany of the flowering plants of North America is 
well understood and recorded in numerous local manuals and larger works of a mono- 
graphic nature, covering the entire country. The following list will enable the stu- 
dent of hayfever to select the volumes necessary to the region in which he is working. 

Roger P. Wodehouse 16 Hay fever Plants 

The general principles of plant classification may be found in many elementary 
textbooks of botany (e.g., SINNOTT 1935) but they are more fully treated in the few 
books which are devoted to the general subject of taxonomy alone. Such a work is 
that of SWINGLE (1934). The first part of this book sets forth and illustrates the prin- 
ciples on which systematic botany is based; the second describes about sixty families 
of flowering plants, including some of those of special interest to the student of hay- 
fever. Others which may be mentioned are J. C. WILLIS (1908) which discusses prin- 
ciples of taxonomy and systems of classification, with suggestions to collectors ; and 
HITCHCOCK (1925) which is an excellent guide to plant collection and study. These 
and other such books are designed to explain taxonomy rather than to serve as tax- 

For the identification of plants encountered in botanical surveys it is generally 
necessary to turn to the standard manuals of botany or local floras. Occasionally one 
venturing into this field is deterred from the use of these books by the difficulties which 
appear to confront the uninitiated in the highly technical language in which such books 
are generally written. They make use of many words which are not encountered in 
ordinary language, it is true, but these are logical in their meaning, and use in their 
construction only a few simple roots which occur over and over again, so that the 
mastery of such words is not difficult after the first few have been learned. Such technical 
expressions are necessary in the interests of brevity and accuracy; their meanings 
have been conventionally agreed upon and are restated in the glossaries which accom- 
pany most taxonomic works. Rather than be deterred from the use of such books on 
account of their technical language, one should welcome the sense of security which 
conies from the use of precise language admitting of no ambiguity. Moreover there 
is no alternative for those who would understand even the elements of taxonomic 
botany. Many so-called popular books, written probably honestly, attempt to provide 
an avenue of escape, excusing their existence by capitalizing the imaginary difficulties 
and dangers of technical language. But for the hayfever botanist these will be found 
only a snare for, being written largely for the aesthetic appeal that flowers may make 
to the dilettanti, they generally omit from discussion the mundane weeds and most 
other plants of economic importance, devoting their attention to those plants which 
offer a supposedly more aesthetic appeal through their pretty flowers, of little interest 
to the student of hayfever. Some even omit entirely the two great hayfever-plant 
families, the composites and grasses, as being too difficult, which they probably are. 
For this purpose there are many excellent manuals and floras. 

Northeastern United States: The "New Manual of Botany" (GRAY 1908) is 
perhaps the most famous of all botanical manuals. It was first published by ASA GRAY 
of Harvard University in 1848. It has been repeatedly revised and extended, and is 
now in its seventh edition, revised by B. L. ROBINSON and M. L. FERNALD. The edition 
is at present out of print but the book is undergoing still another revision under the 
direction of Dr. FERNALD. The area covered by the present edition extends from 
Newfoundland to the southern boundary of Virginia and westward along the southern 
boundaries of Kentucky, Missouri and Kansas to the 96th meridian, including adjacent 
parts of Canada. It is illustrated with 1036 small figures designed to bring out the 
technical characters of most families and genera. 

"The Illustrated Flora of the Northern United States" by BRITTON and BROWN 
(1913) is a much larger work than GRAY'S manual, in three volumes with a total of 
1652 pages and 4666 illustrations. Practically every species is illustrated, which 
greatly facilitates their identification. Its area is about the same as that of GRAY'S 
manual, extending from the Atlantic coast westward to the 102nd meridian and south 
to the southern boundaries of North Carolina, Tennessee, Missouri and Kansas. 

"The Manual of the Flora of the Northern United States and Canada" by N. L. 
BRITTON (1907) is an unillustrated abridgement of the Illustrated Flora, covering 
the same area. 

Southeastern States: "Flora of the Southeastern United States" by JOHN K. 
SMALL (1913) covers the area immediately south of that covered by the Illustrated 
Flora, including Florida and the Gulf coast, and west to the one hundredth meridian. 

Chapter I 17 The Botany 

The book is now out of print and difficult to obtain but has been largely replaced by 
"The Manual of the Southeastern Flora" by the same author (SMALL 1933). This 
book is a great improvement over the earlier volume. Each genus is illustrated by 
sketches of dissections of representative species setting forth important diagnostic 
and anatomical features. The area covered, however, is somewhat less extended than 
that of the earlier volume. It includes the plants which grow naturally south of the 
northern boundaries of North Carolina and Tennessee and east of the Mississippi 

For the southeastern region there is the excellent little "Flora of the District 
of Columbia and Vicinity" by HITCHCOCK and STANDLEY (1916), almost nontechnical 
but complete. 

Central States: The "Flora of the Prairies and Plains of Central North America" 
by RYDBERG (1932), as stated in its preface, aims to be a complete manual of the 
flowering plants and ferns and their allies of the states of Kansas, Nebraska, Iowa, 
Minnesota, South Dakota, North Dakota, and of southern Manitoba and southeastern 
Saskatchewan. It includes also most of the species occurring in the prairie regions of 
Illinois, southern Wisconsin and northern Missouri, and on the plains of eastern Colo- 
rado and eastern Montana. The volume is an exceptionally fine piece of work, the last 
by its great author whose untimely death occurred while the book was still in press. It 
contains 600 figures illustrating representative species of as many genera. 

The state of Kansas is well served by GATES (1936, 1940, 1941), three volumes 
dealing with the Grasses in Kansas, an Annotated List of the Plants of Kansas and 
the Weeds in Kansas. 

The state of Oklahoma is well served by the Oklahoma Flora by T. R. STEMEN 
and W. S. MYERS (1937), but from this volume the grasses are omitted. 

Rocky Mountain Region: This region is well served by the Flora of the Rocky 
Mountains by RYDBERG (1917) covering the states of Utah, Colorado, Wyoming, 
Idaho, Montana, and adjacent parts of Canada, the Dakotas and Nebraska. The work 
is a complete flora, unillustrated. The "New Manual of Botany of the Central Rocky 
Mountains" by COULTER and NELSON (1909) is a revision by NELSON of COULTER'S 
Manual of Rocky Mountain Botany, 1885. "The purpose has been to use Colorado 
as the center of the flora included in the manual and to present the complete flora of 
that state, of Wyoming, of Yellowstone Park, and of the Black Hills of South Dakota ; 
also to include most of Montana, southern Idaho, and the eastern half of Utah, and 
the northern half of New Mexico and adjacent Arizona". The book, though old, is 
still serviceable in its area. 

Southwest: "Botany of Western Texas" by COULTER (1894) is the only book 
devoted to the flora of western Texas. The "Flora of New Mexico" by WOOTON and 
STANDLEY (1915) is an unillustrated volume, listing without description, all species 
(2971) known to occur within the boundaries of New Mexico. The distribution of 
each species within the state and its range outside, and other items of interest to the 
hayfever botanist are given. "The Flowering Plants and Ferns of Arizona" by 
KEARNEY and PEEBLES (1942) is an illustrated flora of the state, published by the 
U. S. Department of Agriculture. It is a splendid volume, complete and authoritative. 
The section of the Compositae is contributed by S. F. BLAKE and that on the grasses 
by JASON R. SWALLEN, based on HITCHCOCK'S Manual of the Grasses. The "Flora 
of Utah and Nevada" by TIDESTROM (1925) presents a discussion of the ecological 
aspects of the region and a systematic list of the flowering plants without description, 
but giving their distribution and habitats. 

Pacific Coast: The "Illustrated Flora of the Pacific States" by ABRAMS (1923) is 
designed to be an authentic reference book covering the flora of Washington, Oregon 
and California, patterned after the Illustrated Flora of the Northern United States 
by BRITTON and BROWN. When completed it is proposed to fill three volumes. So far, 
however, only the first volume has been published. It includes such groups of special 
interest to the student of hayfever, as the grass, willow, walnut, birch, beech, and elm 

Roger P. Wodehouse 18 Hayfever Plants 

families. The volume comprises 557 pages with 1299 figures illustrating practically 
every species described. 

The "Manual of the Flowering Plants of California" by JEPSON (1925) is an 
admirable and extremely useful volume. It comprises 1238 pages with 1023 figures 
designed to illustrate the important diagnostic features of the species described. 

The northern part of the Pacific coast region is covered by several useful books. 
A "Flora of Northwest America" by HOWELL (1903) describes the plants of Wash- 
ington, Oregon and western Idaho. Of more restricted range is the "Flora of Southern 
Washington and adjacent Idaho" by PIPER and BEATTIE (1914). Serving essentially 
the same region is the more recent and very excellent flora by HAROLD ST. JOHN 
(1937). The "Flora of the Northwest Coast" by PIPER and BEATTIE (1915) covers 
the region from the summit of the Cascade Mountains to the Pacific Ocean from the 
49th parallel across the northern portion of Vancouver Island to the northern boundary 
of Lane County, Oregon. The "Flora of the State of Washington" by PIPER (1906) 
presents "An annotated catalogue of the species of vascular plants of Washington." 
The species are not described, but their habitat, range and zonal distribution are given. 
The volume comprises 637 pages with 22 plates, the latter largely of an ecological 
nature, as are also the first 75 pages, which are devoted to a study of the region. 

Cultivated Plants: It is unfortunate that none of the manuals and floras listed 
above gives more than passing reference to the cultivated species, since it is among 
these that one most frequently encounters the minor or incidental causes of hayfever. 
As we have already seen, the general rule that showy plants do not cause hayfever, 
can not be applied too strictly to cultivated plants ; it is one thing to pass a plant in 
the field but quite another to handle it, as we are prone to do with cultivated plants, and 
live with it in the same room. However these are all provided for in a number of 
very excellent books. The "Manual of Cultivated Plants" by BAILEY (1924) describes 
the species most commonly cultivated in America, for whatever purpose, and whether 
outdoors or under glass, accounting for 3665 species in 170 families. Also included are 
many species formerly cultivated, now abandoned but become more or less well estab- 
lished in the wild. The book comprises 851 pages and 14 full page figures illustrating 
typical species from some of the families. Though the volume is not otherwise illus- 
trated, it possesses such excellent keys and concise descriptions that identifications are 
not difficult. The book, however, does not give much consideration to the innumerable 
horticultural varieties which make the botany of cultivated plants so difficult and com- 
plex. These, however, are fully described in that monumental work, "The Standard 
Cyclopedia of Horticulture" by the same author (BAILEY 1914), accounting for 
20,602 species with their varieties. The "Field, Forest and Garden Botany" by GRAY 
(1895), as revised by BAILEY, is a simple introduction to the common plants east of 
the 100th meridian. Though both wild and cultivated plants are included the em- 
phasis is on the latter. REHDER (1940), "Manual of the Cultivated Trees and Shrubs 
Hardy in North America" is a book of 996 pages dealing with the woody plants, 
unillustrated, but gives the times of flowering and the zones in which the plants are 
hardy. "The Cultivated Conifers of North America" by BAILEY (1933) is a splendid 
volume including all species of conifers known in cultivation north of Mexico. The 
word, 'cultivated', is interpreted in its broadest sense, including many native species 
which are only occasionally found in cultivation. Thirty-nine genera and 275 species 
are discussed and 57 others incidentally recorded. The volume comprises 403 pages, 
48 plates and 114 other figures. The plates and figures are a delight to behold. 

The Trees : There are many excellent tree books but the greatest of them all, in 
fact one of the greatest books ever produced in this country is the "Silva of North 
America" by C. S. SARGENT (1897). The book is in 14 volumes comprising 2185 pages 
and 740 full-page lithographic plates. Each species is illustrated and described, with 
notes on its ecology and economic importance. Unfortunately few people can afford 
the luxury of owning such a book as this, and it is scarcely to be found outside of the 
larger libraries. An excellent substitute, however, is found in the "Manual of the 
Trees of North America" by the same author (SARGENT 1922). This is the standard 

Chapter I 19 The Botany 

condensed reference book on trees in this country. It brings into convenient form the 
materials of the Silva. It comprises 910 pages. Each species is fully described, with 
ecological notes and detailed account of its distribution within its range, which is a 
valuable feature not found in any of the manuals and floras, which are content to merely 
outline the ranges. Each species is illustrated, with a total of 783 figures, of more 
than passing excellence, by CHARLES EDWARD FAXON and MARY W. GILL. Cultivated 
trees are not treated, only occasionally mentioned in passing. "North American Trees" 
by BRITTON (1908) deals with the trees growing independently of cultivation north of 
Mexico. Each species is illustrated and described in almost non-technical language. 

There are many tree books of a less technical nature, among which may be men- 
tioned JULIA ROGERS (1905), "The Tree Book, a popular Guide to a Knowledge of the 
Trees of North America and their uses in Cultivation", and EMERSON and WEED (1918), 
"Our [American] Trees and how to Know them", an excellent popular book with a 
good photograph and description of each species. 

There are also a number of tree books of limited range, among which should be 
mentioned the "Handbook of the Trees of the Northern States and Canada east of the 
Rocky Mountains" by HOUGH (1907). Most of the species described are illustrated 
to show their habit, leaves, fruit, twigs, and flowers and frequently a section of wood. 
"The Trees of Texas" by LEWIS (1915) is an illustrated manual of the native and in- 
troduced trees of the state. California is well supplied through the several publications 
of JEPSON of which perhaps the most important is "The Silva of California" ( JEPSON 
1910), a large and complete technical volume well illustrated. The "Trees of Cali- 
fornia" by the same author (JEPSON 1909) is a small popular manual with many illus- 

Monographs of Restricted Groups: Of special interest to the student of hayfever 
is "The Phylogenetic Method in Taxonomy" by HALL and CLEMENTS (1923). It is a 
treatise of the North American species of Artemisia, Chrysothamnus and Atriplex. The 
species are minutely described snowing their relationships, distribution, time of flower- 
ing and importance in hayfever. A purely taxonomic treatment of Artemisia and allied 
genera has been published in the North American Flora by RYDBERG (1916). Also 
published in the North American flora is the " Ambrosiaceae" by RYDBERG (1922) and 
"Xanthium" by MILLSPAUGH and SHERFF (1922) which should be regarded as the 
standard texts on the tribe Ambrosieae. 

The "Manual of the Grasses of the United States" by HITCHCOCK (1935) is recog- 
nized as the final authority on this group. The book comprises 1040 pages and 1696 
figures. The species are fully described, most of them illustrated and accompanied by 
maps showing their distribution in the United States. A valuable feature of the work 
is that English names are given for the species as far as these are known or exist, 
standardized by the late F. C. COVILLE, formerly a member of the American Joint Com- 
mittee on Horticultural Nomenclature and one of the authors of Standardized Plant 
names. Both the technical and vernacular names used in this book should be recog- 
nized as the standards. 

"The Genera of the Grasses of the United States" is a similar but much smaller 
work by HITCHCOCK (1920). Under the generic headings most economic species are 
described including practically all those of interest to the student of hayfever. 

Of interest to those who wish to follow up the subjects of taxonomy and floristics 
in greater detail is the recently published "Geographical Guide to the Floras of the 
World" by BLAKE and ATWOOD (1942). This is an annotated list of all important taxo- 
nomic publications throughout the world, with special reference to useful plants and 
common plant names. 

Those who wish to go deeply into the subject of pollen identification will find 
much useful information in ERDTMAN (1943), Pollen Analysis. Though this book 
deals primarily with fossil pollen, the principles laid down in it are as readily applicable 
to the study of atmospheric pollen of the present. 

Chapter II 

The gymnosperms may be distinguished by their seeds which are borne 
naked on the upper surface of the scales of cones instead of in a closed ovary 
in a flower. The pollen is borne in little anther sacs on the under surface of 
scales of smaller cones. In fertilization the pollen is brought directly in 
contact with the ovule. Almost never are the two sexes combined in the 
same cones, but the pistillate and staminate cones are borne sometimes both 
on the same plant, sometimes on different plants. 

All species are wind pollinated and many of them are characterized by 
the enormous quantities of pollen that they shed. Fortunately, however, 
the pollen of most species is quite harmless in hayfever. The gymnosperms 
are generally tall stately trees with needle-shaped leaves. But there are 
some notable exceptions. Some are merely shrubs, like the little mugo 
pine of parks and gardens ; the larches are completely deciduous ; the maiden- 
hair tree has broad flat fan-shaped leaves and some of the Southern Hemi- 
sphere podocarps have leaves as broad as our ordinary hardwood trees. 
Phyllocladus has all its leaves reduced to scales which soon drop off, their 
place being taken by specialized flattened branches which are green and 
function like leaves. Exceptions of this kind, however, are to be expected 
in a group as old as the gymnosperms. They are the records of the vicissi- 
tudes of their ancient past. 

The gymnosperms are, indeed, an immensely ancient group. They were 
represented in past geological ages by such mighty races of trees as the 
Cycadofilicales and Cordaitales of the Carboniferous period and the Ben- 
nettitales of the Mesozoic era. They are today represented by four living 
groups, the Cycadalcs, including the sago palm and comfort root, the Gink- 
goales, itself a mighty phylum in past geological ages but of which only the 
maidenhair tree remains among the living, the Conijerales, comprising the 
pines, firs and larches and in fact all the better known gymnosperms ; and 
the Gnetales, a small and poorly understood group of desert and tropical 
countries, but now famous for Ephedra which is the source of the popular 
drug ephedrin. Of these only the following two families are of interest to 
students of hayfever. 

Ginkgoaceae (The Ginkgo Family) 

Ginkgo or maidenhair tree (Ginkgo biloba L. or Salisburia adiantijolia 
Sm.) is a large and beautiful tree, generally with tall straight central axis 
bearing large heavy side branches slanting obliquely upwards. Its leaves 
are broad and fan shaped, resembling the leaflets of the maidenhair fern. 

The trees are dioecious, the staminate and pistillate cones occurring in 
separate trees. They shed large quantities of light pollen which has occa- 
sionally been suspected of causing hayfever. 

The pollen grains (fig. 8B) are boat shaped, 27 to 32 /* long, provided 
with a single deep longitudinal furrow, the exine is thin and smooth. The 

Chapter II 21 Gymnosperms 

primitive character of this grain is entirely in harmony with the position 
assigned to this species among the most primitive species of living gymno- 

Ginkgo is native of Japan and eastern China where it is a favorite tree 
for planting in the temple gardens. It has been called by DARWIN a "living 
fossil," for it is the last of a mighty race which flourished in the early and 
middle periods of the Mesozoic, probably starting their career even as long 
ago as the Permian in association with the Cordaitales and Cycadofilicales. 
This single remaining species is not known to occur in the wild state ; indeed 
it has been said to owe its survival to the fact that for centuries it has been 
regarded as sacred by the Chinese, and piously planted and cared for by 
the Buddhist priests. Recently, however, its cultural value has become 
widely recognized and it is now used as an ornamental tree almost through- 
out the civilized world. 

Goni ferae 

The family of the Conijerae includes trees and shrubs with flat needle- 
shaped leaves, such as the pines, firs, junipers, and yews. They are mostly 
evergreen, inhabitants of temperate regions. 

The members of the family are most properly grouped into the following tribes : 
(1) Araucarineae, the Southern Hemisphere pines, (2) P odo car pine ae, the podocarps 
and their allies, mostly of the southern hemisphere, (3) Abictineae, comprising the 
pines, firs, spruces and larches, mostly of the north temperate region, (4) Cupressineae, 
including the junipers, cypress and allied forms, (5) Taxodineae, including the bald 
cypress (Taxodium) and sequoias, (6) Taxincac, including the yews. The six tribes 
are fairly distinct and such relationships as exist between them are obscure and con- 

Most species shed enormous quantities of pollen which is notorious for the great 
distances it is carried by the wind, yet only a few, principally members of the Cupressi- 
neae, have been shown to cause hayfever. Their pollen, however, is among the most 
frequent and conspicuous elements caught on atmospheric pollen plates. 

Abietineae (The Pines, Spruces and Firs) 

On the basis of their pollen grain structure the Abictineae may be divided 
into two, the winged-grained and the wingless-grained. The pollen grains 
of the winged-grained Abietineae (fig. 8A,F,G) are characterized by the 
possession of a single longitudinal germinal furrow on the ventral side. It 
is usually only vaguely defined but is generally flanked by two conspicuous 
air-filled bladders. When the grains are moist they spread apart and expose 
the furrow, and when they are dry they press tightly together over the fur- 
row as if to check further loss of water. The bladders also undoubtedly 
serve to give the grains greater atmospheric buoyancy for, in spite of their 
large size, they are known to be transported great distances by the wind. 
Generally there are two bladders symmetrically arranged, but occasional 
grains may be found in the pollen of most species with three, four, or more 
bladders, and the grains of some of the firs have a single bladder encircling 
the furrow in the form of a frill. On the other hand the pollen grains of 
the larches and some of the hemlocks (fig. 8D,E) are without bladders. 

Roger P. Wodehouse 


Hayfever Plants 

Pinus (The Pines) 

The pines are all evergreen with needle-shaped leaves fascicled in axil- 
lary clusters of one to five enclosed at their base by a membranous sheath. 
They are monoecious with the staminate cones clustered at the base of 
leafy growing shoots of the year, small and catkin like, yellow, orange or 
scarlet, composed of numerous spirally arranged two-celled anthers (fig. 


The pollen grains range from 44 to 65/x, in diameter, exclusive of the 

bladders. The latter are rounded when expanded, and retain most of their 
convexity even when tightly closed over the furrow (fig. 8F). 

FIG. 7. Cones of conifers. A, Hemlock 
(Tsuga) pistillate and B, a single scale bearing its 
two seeds. C, White pine, staminate cone and D, 

Pine pollen has occasionally been reported to cause hayfever (e.g., 
WALKER 1921, DAVISON, LOWANCE and DURHAM 1934), but it is doubtful 
if these cases have been fully substantiated. More recently ROWE (1939) 
has reported a case of pine pollen allergy which seems to leave no doubt 
that pine pollen can be allergenic. Significant skin reactions were obtained 
with this case to the pollens of Monterey, white, knob-cone, Austrian, sugar, 
bishop, yellow, Scotch and tamarack pines. ROWE states, "Pine pollen 
allergy productive of bronchial asthma and associated with large scratch 
skin reactions is recorded for the first time in the literature." Presumably 
the earlier records are not regarded by him as authentic. The rarity of 
such cases is in a way surprising for pine pollen is among the most abundant 
in the atmosphere. 

Chapter II 23 Gymnosperms 

The genus comprises about 70 species, trees and shrubs of the northern hemisphere. 
The species can be conveniently grouped into two sections, the soft pines and the pitch 
pines. The former are characterized by soft close grained and light colored wood, their 
leaves generally in clusters of five. The pitch pines have usually heavy coarse-grained 
wood, often dark colored, and their leaves generally in clusters of two. 

Among the soft pines the best known, and formerly one of the commonest trees 
throughout eastern North America, is the white or Weymouth pine (Pinus Strobus L.) 
It is a tall timber tree reaching a height of 225 feet, flowering in June. 

Among the pitch pines the Jersey or scrub pine (P. virginiana Mill.) is the common 
tree of the pine barrens of New Jersey and Long Island. It is generally a small tree 
but reaches its best development in the western part of its range, sometimes attaining 
a height of 110 feet. Flowering in May the trees shed large quantities of pollen. 

A species similar to and often associated with the Jersey pine is the pitch or torch 
pine (P. rigida Mill.). It is a small tree reaching a height of only about 80 feet. 

In the Rocky Mountain region are a number of very beautiful species which have 
occasionally been thought to cause hayfever. Among them is the western pitch pine 
or bull pine (P. scopulorum Lemm.)- It is a large tree attaining a height of 120 feet 
with leaves two or three in a cluster. Its seed-bearing cones are dense and woody, 
their scales thickened towards their ends and tipped with a prickle. 

Many of our native pines and several European species appear frequently in cul- 
tivation. One of the commonest of the introduced species is the beautiful Austrian pine 
(P. nigra Arnold, P. Laricio Poir.). It is a large tree of variable habit, frequently 
reaching 100 feet in height, with dark green leaves 3 to 7 inches long in fascicles of 
two. It occurs in several geographical and horticultural forms. One of those most 
generally cultivated is the variety austriaca Asch. & Graeb. (P. nigricans Hort.), a 
broad headed form generally with a flat top. The species is native of southeastern 
Europe but is widely planted. 

Also frequently cultivated in the East is the Scotch pine (P. sylvestris L.). It is 
a large forest tree native of Europe and Asia. 

A great favorite, especially for planting around houses and in small gardens, is the 
little mugo or Swiss mountain-pine (P. Mugo Turra., P. montana Mill.). It is ex- 
tremely various, occurring as a low prostrate shrub or as a pyramidal tree reaching 
80 feet in height. It is native of the mountains of central and southern Europe, but is 
extensively cultivated elsewhere, especially in its smaller varieties. It flowers in May 
shedding fairly large amounts of pollen. 

Picea (The Spruces) 

The spruces comprise about 40 species of north temperate and sub- 
arctic regions, of tall pyramidal trees with whorled branches. Their leaves 
are generally four angled and distributed rather evenly around the twigs. 

The pollen grains (fig. 8A) are similar to those of Pinus, except that 
they are larger, ranging in the different species from about 68 to 91 /* in 
diameter, exclusive of the bladders; also the latter have a tendency to be 
flattened from below, and when they are pressed together, as the grains 
dry, they generally become flattened or even concaved on their proximal 

Perhaps the best known species, and the one most commonly cultivated, 
is the Norway spruce (P. Abies Karst.) , native of Europe. Our commonest 
native species in the East are the white spruce (P. canadensis B.S.P.) and 
the red spruce (P. rubens Sarg.). In the West are found such forms as 
the Engelmann blue spruce (P. Engelmanni Engelm.) and the Sitka spruce 
(P. sitchensis Carr.), and in the Rocky Mountain region the beautiful 
Colorado blue spruce (P. pungens Engelm.). 

Roger P. Wodehouse 


Hayfever Plants 

The spruces are among our commonest evergreen trees, and their pollen 
is nearly always caught in abundance on pollen slides in May and June, but 
it has not been shown to cause hayfever. 

FIG. 8. POLLEN GRAINS OF GYMNOSPERMS: A. Upper left, Spruce (Picea canaden- 
sis) ; B. Upper right, Ginkgo (Ginkgo biloba} ; C. Right second from upper, Red cedar 
(Juniperus virginiana) ; D. Middle left, Hemlock (Tsuga canadensis) ; E. Middle right, 
Larch (Larix laricina) ; F. Lower left, White pine (Pinus strobus) ; G. Lower right, 
Fir (Abies). All magnified 700 times. 

Chapter II 25 Gymnosperms 

Abies (The Firs) 

The firs comprise about 30 species of tall pyramidal trees of north tem- 
perate and sub-polar regions, with spreading flat leaves appearing to be 
two ranked. 

Their pollen grains are similar to those of the pines and spruces but 
larger than either, ranging in the different species from 78 to 101 /x in 
diameter, exclusive of the bladders (fig. 8G). The large size of these 
grains restricts their dissemination by wind for they are seldom caught on 
atmospheric plates, nor is their pollen known to cause hayfever. 

Several species are cultivated. The white fir (A. concolor Lindl. & 
Gord.), a native western species, is much used in landscaping. The com- 
mon or Canada balsam (A. balsamea Mill.) is abundant throughout a large 
part of Canada. On the Pacific coast are several species of particularly 
beautiful and imposing trees. 

Tsuga (The Hemlocks) 

The hemlocks are tall pyramidal trees with gracefully nodding leading 
shoot. The leaves are short and flat, scattered on the twigs but spreading 
horizontally so as to appear two ranked. The genus comprises about nine 
species of temperate regions. In America the most widely distributed is 
the common hemlock ( T. canadensis Carr. ) , growing naturally throughout 
the northeastern United States and Canada. On the Pacific coast are found 
the western hemlock (T. heterophylla Sarg.) and the mountain or black 
hemlock ( T. Mcrtensiana Sarg. ) , both extending from Alaska to California. 

Two types of pollen grain occur among the species of this genus. The 
grains of T. canadensis and T. heterophylla are without lateral bladders or 
have them represented by only a rudimentary frill (fig. 8D), while those 
of T. Mertensiana are generally provided with two well developed bladders 
causing the grains to resemble those of the firs, but they are smaller, 57 to 
65 fjL in diameter. The grains of T. heterophylla are about 50 to 55 /x in 
diameter, those of T. canadensis 60 to 85 /x. Both are somewhat flattened 
dorsiventrally, more so on the dorsal than the ventral side. The exine of 
the dorsal surface is thick and coarsely reticulately corrugated, that of the 
ventral thinner and merely granular. Frequently the margin at the junc- 
tion of the two is thrown into a puffy frill suggesting a rudimentary bladder 
encircling the grain. 

Hemlock pollen, in spite of the large size of the grains, is frequently 
caught on atmospheric pollen slides, and has occasionally been suspected of 
causing hayfever. 

Cupressineae (The Junipers and their Allies) 

The Cupressineae comprise about seven genera of trees and shrubs, all 
rather closely related and including, besides the two described below, the 
Cypresses (Cupressus), the white cedars or arborvitae (Thuja) and the 
incense cedar (Libocedrus). They are distinguished by their small opposite 
or whorled leaves which are usually scale like, and their small pistillate 

Roger P. Wodehouse 26 Hayfever Plants 

:ones with few scales. Their pollen grains are spheroidal with thin flecked 
>xine and greatly thickened intine and with only a small and inconspicuous 
jerm pore or none at all. 

Since it has already been shown that members of two genera of this 
:ribe cause hayfever, all should be regarded as potential causes until proved 

Juniperus (Jumper, Savin, Red Cedar) 

The junipers are evergreen trees or shrubs usually with thin shreddy 
Dark and small leaves which may be sharp pointed and spreading or scale 
ike and closely appressed. The trees are principally dioecious, though some 
species are partly monoecious. The staminate cones (fig. 9) are minute, 

FIG. 9. Staminate cone of Juniperus. 

)orne in short axillary or terminal branches from buds formed the previous 
mtumn on branches of the year. The fruit is a berry-like succulent, blue, 
)lueblack or red strobile, containing one to six bony wingless seeds. 

Most species produce surprisingly large amounts of pollen which is shed 
generally very early in spring or, in the milder regions, in mid winter or 
iven late fall. 

The grains (fig. 8C) are spheroidal, 20.5 to 30.0 /x in diameter, exine 
:hin and irregularly flecked with granules. Occasional grains are found 
provided with a single small circular germ pore. The intine is excessively 
:hick and, expanding upon the absorption of moisture, ruptures and throws 
Dff the exine, so that cast exines are as often found as intact grains. 

The genus comprises about 40 species widely distributed throughout the northern 
lemisphere. The American species fall into two rather distinct groups or subgenera des- 
gnated as Oxycedrus and Sabina. Those of the first group have linear-lanceolate prickle- 
ipped leaves, arranged in three series, and spreading ; and their cones axillary, the pis- 
illate maturing in the third year to form bright blue subglobose berries. These are 
egarded as the true junipers including, for example, the common juniper (/. com- 
nunis). Those of the second group have mostly scale like leaves arranged in two or 
hree series and closely appressed, except on young plants and vigorous shoots where 
hey may resemble the leaves of the first group, and their cones are terminal on short 
ixillary branches, the pistillate maturing into red, reddish brown, blue or black fruit; 

Chapter II 27 Gymnosperms 

these are the cedars or savins, for example the red cedar (/. virginiana}. Some authors 
prefer to treat the two groups as separate genera, in which case Oxycedrus, since it is 
regarded as comprising the true junipers, takes the name Juniperus, while the others 
are called Sabina. It is the opinion of the present author, however, that the two groups 
are too closely related to bear separation into different genera. 

The most important in hayfever is the mountain cedar, Mexican cedar 
or rock cedar (/. mexicana Spreng., /. sabinoides Nees). It is a small 
tree, occasionally reaching 100 feet, but generally little more than a large 
shrub, forming a wide round topped, open and irregular or narrow pyra- 
midal head. This species is extremely abundant on the lime-stone hills of 
Texas. "The plant is more abundant along the rather rugged escarpment 
which borders the southern edge of the Edwards Plateau. Here it is very 
abundant and practically the only juniper" (THARP 1937). The species is 
generally regarded as dioecious, but Professor THARP states that it is not 
entirely. "Occasionally one finds a few berries on a staminate tree. I do 
not recall having noted any staminate cones on a pistillate plant, however". 
Flowering in December and January, the tree produces enormous quantities 
of pollen which is known to cause a serious type of winter hayfever. This 
was first brought to the attention of the medical profession by KEY (1918). 
KAHN and GROTHAUS (1931) find that in parts of Texas mountain cedar 
pollen is as important as ragweed pollen is in the East, its effects lasting 
sometimes eight weeks. 

The Texas mountain cedar is an outstanding example of a plant that 
has been made to cause hayfever by human activity. Of it WILLIS and 
DEGLER (1939) say, "Some old settlers claim that years ago there were 
comparatively few cedar trees in Texas, and that the hills were covered 
largely with high grass. This grassland was used for grazing ; over-grazing 
without giving the land proper rest periods probably gave the cedar growth 
its start. It then became the practice to burn the grass (and incidentally 
the cedar) off at definite intervals. As this area became more thickly popu- 
lated fences were erected ; over-grazing became more intense and the danger 
of burning the fences stopped the practice of burning, until now many of 
the Texas hills are covered with a very thick growth of cedars". 

The common red cedar or juniper (/. virginiana L.) also called red savin, Carolina 
cedar or pencil wood, is the most abundant juniper throughout the eastern United 
States and Canada, frequenting fields and pastures and dry rocky places. It is generally 
of a slender columnar form, with fragrant red heart wood. It is naturally variable 
and has given rise to many cultivated varieties. It flowers very early in spring, about 
March or April. Its pollen has been shown to interreact with that of the Texas spe- 
cies (KAHN and GROTHAUS 1931), and it appears likely to cause some hayfever, partic- 
ularly in Georgia and Tennessee where the species is most abundant and reaches its 
best development. 

Several other species of Juniper are occasionally encountered in hayfever literature 
and, since the pollens of all seem to interreact more or less perfectly, it is possible that 
they cause some hayfever. Among these should be mentioned the common juniper 
(/. communis L.) also called horse savin, hackmatack and aiten. It is a shrub or small 
tree of pyramidal habit, not over 30 feet in height, with leaves all spreading and prickle 
tipped. It flowers in April or May. Its fruit, the malneat berries of commerce used 
for flavoring gin, ripen in October. The species is extremely variable and has given 
rise to several varieties much prized in cultivation. 

Roger P. Wodehouse 28 Hayfever Plants 

The cherrystone juniper (/. monosperma Sarg.) is a shrub or small tree of south- 
ern Colorado, New Mexico, Arizona and Utah, and the alligator or checker-bark 
juniper (/. pachyphlaea Torr.) is generally a small tree, 50 to 60 feet high, of Northern 
Texas, New Mexico and Arizona. Both species flower very early in spring, February 
or March, and are regarded as possible causes of hayfever in New Mexico and Arizona. 
The Utah juniper (/. utahensis Lemm.) occurring in the Rocky Mountain region and 
westward to southern California, and the Rocky Mountain juniper (/. scopulorutn 
Sarg.) occurring in the Rocky Mountain region and westward to British Columbia, are 
believed to occasionally cause hayfever. 

Of special interest is the Bermuda cedar (/. bennudiana L., /. barbadensis L., Sabma 
bermudiana Antoine). It is an irregular and widely branched tree, reaching a height 
of about 70 feet and a trunk diameter of four feet, with thin gray flaky bark. The 
leaves of young plants and shoots are spreading and sharp pointed but those of mature 
twigs are scale like and closely appressed in four ranks giving the twigs a four sided 
appearance. The trees flower in March and April shedding large quantities of pollen 
which causes almost the only hayfever there is in Bermuda (HODGSON 1935, GAY, 
CURTIS and NORRIS 1941). 

Bermuda cedar is the most abundant tree of Bermuda and apparently does not 
grow outside of the islands, although it has been reported as growing in the West 
Indies. A similar and very closely related species, commonly called Cuban cedar (/. 
lucayana Britt.) is found in the northern Bahama Islands and Cuba. This species 
is also known as /. barbadensis Sarg. and Sabina barbadensis Small, and appears to be 
the species referred to by KAHN and GROTHAUS (1930) and reported by them to prob- 
ably cause some hayfever in Florida. 

Ghamaecyparis (Cypress and Retinispora) 

The cypresses are tall pyramidal trees resembling the junipers. The 
staminate and pistillate cones are borne on the same tree but on different 

The genus comprises about six species, confined to the Atlantic and 
Pacific coasts of North America, and Japan and Formosa. They are closely 
related to the junipers but may be distinguished by their woody cones in 
place of the berry-like fruits of the junipers. They are also closely related 
to the genus Cupressus, another group of cypresses to which the Monterey 
cypress belongs, but may be distinguished from them by the fact that the 
cones of Cupressus mature only in their second year while those of Chamae- 
cyparis mature in their first. Nevertheless the two genera are frequently 
joined as one under the name, Cypress. 

There are many varieties, shrubby forms, of both the native and Asiatic 
species in cultivation known as retinisporas among the horticulturists, using 
the name of an old genus which included the juvenile stages of Chamae- 
cyparis and Thuja. 

On account of the closeness of their relationship with the junipers it is 
likely that the cypresses have the same capacity to cause hayfever, but only 
Lawson cypress or Port Orford cedar (Chamaecyparis Lawsoniana Parl., 
Cupressus fragrans Kell.) has been shown to do so. This is a noble forest 
tree occasionally reaching 200 feet in height, with a pyramidal head of 
bright green leaves. In its natural habitat it is found only on moist hillsides 
and canyons in southern Oregon and northern California. It has, how- 
ever, given rise to many prized varieties which are cultivated throughout 
the warm moist regions of the United States under such names as cream 

Chapter II 29 Gymnosperms 

cypress, scarab cypress, silver queen and steel cypress. It flowers princi- 
pally in May, shedding large amounts of pollen which has been shown by 
BLACK (1929) to interreact perfectly with that of Texas mountain cedar 
and to be a contributing cause of hay fever. 

The pollen grains of Lawson cypress are similar to those of the junipers, 
but are extremely various in size, 28.6 to 39 /A in diameter ; and generally 
they exhibit a small germinal papilla. The exine may be almost entirely 
covered with minute flecks or nearly smooth. 

Chapter III 


The angiosperms may be distinguished by their universal habit of bear- 
ing their seeds in closed ovaries instead of naked on cone scales as do the 
gymnosperms. Their pollen does not come in direct contact with the ovule ; 
instead it is deposited on the stigma and its tube must penetrate the tissues 
of the pistil to reach the ovule. The fructifications of the angiosperms are 

FIG. 10. Lily (Lt'/ww) seedlings, 
an example of a Monocotyledon. 

true flowers. Basically the flower is a beautiful and attractive structure, and 
these characters are with it primitive. Witness, for example, the beautiful 
flowers of magnolia, the water lily or buttercup, all three of which are among 
the most primitive angiosperms. There appears to be little doubt that the 
angiosperm flower arose in association with possibly even as the result of 
pollination by insects. It is therefore basically and primitively a mechanism 
adapted to securing pollination by insects. The wind-pollinated forms are 
always derivative and never primitive. 

Chapter III 



The angiosperms are arbitrarily divided into two groups, the mono- 
cotyledons and the dicotyledons, so called because the seedlings of the 

FIG. 11. Ragweed (Ambrosia) seedlings, an example of a Dicotyledon, 
majority of the first group seem to produce but a single seed leaf or cotyledon 

FIG. 12. Foliage leaves, examples of Monocotyledons (A,B) and Dicotyledons 
(C,D) : A, Iris, B, Day-flower (Commelina), C, English ivy (Hedera), D, Chrysan- 

(fig. 10) while the seedlings of the majority of the second group produce 
two cotyledons (fig. 11 ). There are many exceptions, and among the more 

Roger P. Wodehouse 32 Hayfever Plants 

primitive members of the groups the dividing line is seen only vaguely and 
has given rise to much controversy. For the most part, however, the two 
groups are quite easily distinguished and appear to be at least partly natural. 
The monocotyledons generally have parallel veined leaves, like those of the 
palms, iris and grasses, while the dicotyledons generally have net veined 
leaves, like these of the oak, lilac and chrysanthemum (fig. 12). The 
dicotyledons may form a cambium in their stem, a thin-growing layer which 
builds up a fresh layer of wood and bark each year, as in the oaks, poplars 
and maples. Monocotyledons never do ; for example the palms are unable 
to enlarge their trunk diameter no matter how tall they grow. The pre- 
vailing form of pollen grain among the monocotyledons has a single germinal 
furrow or pore, except where it has suffered effacement through reduction 
in response to special modes of pollination (fig. 14). The pollen grains of 
the dicotyledons generally have three or more pores or furrows, except the 
reduced forms which have none ; only among some of the more primitive 
members do they have a single one. There are other rules and other excep- 
tions but, for the most part, a little experience will enable one to say at a 
glance to which of the two groups any flowering plant belongs. The palms, 
sedges, lilies, grasses and orchids are examples of monocotyledons, while 
the magnolias, buttercups, maples, roses, oaks and ragweeds are examples 
of dicotyledons. 


To this group belong the cattails, sedges, rushes, palms and grasses 
which are described below, also such well known forms as the lilies, onions, 
trillium, fritillarias and yucca which belong to the lily family; and their 
close relatives, the amaryllis, agave and narcissus of the amaryllis family ; 
and the orchids. These are the most typical monocotyledons, but the group 
also includes the calla, arum, jack-in-the-pulpit and skunk cabbage of the 
arum family; the water plantains and arrowheads of the water-plantain 
family ; and the pondweeds, naiads, eel grass and quillworts of various other 
families, so divergent in form and habit that their association with the other 
members of the monocotyledonous group appears to be arbitrary and un- 
natural. However, such aberrant forms are of little interest to the student of 
hayfever because they are either insect pollinated, or they shed too little 

Typhaceae (The Cattail Family) 
Typha (The Cattails or Cattail Flags, fig. 13) 

The cattails are marsh or aquatic herbs with round stems and long flat 
leaves sheathing at the base. The flowers are minute and densely crowded 
into terminal spikes, the staminate in the upper and the pistillate in the 
lower part of the spike. The flowers themselves are of the simplest struc- 
ture, the staminate consisting of two to seven stamens surrounded by 
bristles which represent a degenerate perianth, and the pistillate similar 
but with a single pistil in place of the stamens. It is this simplicity of floral 
structure that has condemned these plants to the lowly position assigned 
them in most classifications, at the very bottom of the monocotyledonous 

Chapter III 



group. This simplicity, however, is not of a primitive character but due to 
reductions, the sort that always accompany the habit of wind pollination 
among the angiosperms, to which the cattails are very well adapted. 

The genus comprises about 10 species of temperate and tropical regions. Two of 
them, the broad-leaved and narrow-leaved cattails (T. latifolia L. and T. angustifolia 
L.), are common throughout most of North America except the extreme north. The 
two species are similar but the former is more robust. Its leaves are one quarter to one 

FIG. 13. Cattail flag (Typha latifolia}, an ex- 
ample of a Monocotyledon. 

inch broad, its flowering spikes dark brown with the staminate and pistillate portions 
contiguous. It is the more abundant of the two. The narrow-leaved species is more 
slender throughout and its leaves one third to one half inch broad, its flowering spike 
light brown, with the staminate and pistillate portions separated by a short naked inter- 
val of the stem. 

Both species shed enormous quantities of pollen which may be caught on pollen 
slides miles from where the plants are growing, but it appears to be incapable of causing 
hayfever. The pollen grains of both are essentially alike except that those of the 
broad-leaved cattail always occur united in tetrads (fig. 14 E), while those of the 

Roger P. Wodehouse 34- Hayfever Plants 

larrow leaved species are always single (fig. 14 F). The individual grains in either 
:ase are spheroidal or variously irregular in shape, 18 to 30/A in diameter, with thin 
finely reticulate exine and rather thick intine. There is always a single germ pore of ir- 
egular shape and with jagged margins. In the pollen of the broad leaved species all pos- 
sible arrangements of the four cells occur. When the tetrads are flat or squarish the pores 
tend to be all on the same side of the group and toward the outer margins of the cells, 
in the tetrahedral tetrads they tend to be on the part of each cell remote from its con- 
tact with its neighbors of the group. 

Arecaceae (The Palms) 

Some of the palms are suspected of causing hayfever. Though they 
appear to be primarily insect pollinated, there is no doubt that the pollen 
of some may at times become atmospheric. DAVISON, LOWANCE and 
DURHAM (1934) pointed out that the date palm (Phoenix dactylijera L.), 
the coconut palm (Cocos nucifera L.) and the cabbage palm (Sabal) are 
found in Miami, Florida, and they state, "In Florida and possibly along the 
southern coast states, the palms produce sufficient pollen to be considered 
as possible causes of hayfever and hay asthma but we have not been able to 
find reports of any cases caused by this pollen' '. 

PRINCE (SELLERS 1934), reporting from Galveston, Texas, states, "Another plant 
with which we must deal ... is the date palm, a tropical tree that has no definite polli- 
nating season. A great number of these trees occur in our vicinity, and I am told there 
ire several closely related varieties. It is possible to collect as much as half an ounce 
3f very fine light pollen from a single date bloom". There are about a dozen species of 
date in cultivation. One of the commonest ornamental species in the South is the 
Canary Island date (Phoenix canariensis Chaub.). 

Gramineae (The Grass Family) 

The grasses are herbaceous or rarely woody plants, with hollow or solid 
stems, and two-ranked parallel-veined leaves consisting of two parts, the 
lower enveloping the stem as a sheath, and the upper expanding as the 
blade. The flowers are generally perfect, that is producing both stamens 
and pistils, but without functional calyx or corolla, of an inconspicuous 
greenish color, and aggregated in spikes or panicles at the ends of the main 
stem or branches. A few, like the Indian corn, are monoecious with the 
staminate flowers in the tassels at the top of the stem and the pistillate in 
the axils of the leaves lower down on the stem, or like the Indian rice in 
which the spatial orientation is reversed, the pistillate flowers being borne 
at the top of the panicle and the staminate lower down in the same panicle. 

The pollen grains of the grasses, when moist and expanded, are sphe- 
roidal, ovoidal or ellipsoidal, about 20 to 100/x in diameter, though seldom 
over 50/x (fig. 14). The exine is always thin and nearly smooth, but may 
be faintly granular or exceedingly finely reticulate pitted, and is almost free 
from oil. The intine is thick and hyaline. The grains have always a single 
small germ pore approximately circular in outline, provided with a thickened 
rim and a minute operculum which, in the moistened condition, stands off 
from the rim on the bulging pore membrane. When the grains dry the 

Chapter III 



exine collapses irregularly, generally causing the grain to assume an angular 
form, and the operculum is drawn tightly into the mouth of the pore. 

pratense) ; B, Rye (Secale cereale} ; C, Sedge (Carex) ; D, Timothy dry; E, Broad- 
leaved cattail (Typha lattfolia) ; F, Narrow-leaved cattail (T. angustifolia) . All mag- 
nified 1300 times. 

The grasses are entirely wind pollinated unless self pollinated, and their flowers 
are most profoundly modified in adaptation to anemophily. So far reduced are they 
that it is not easy to make comparison between these flowers and those of more typical 

Roger P. Wodehouse 


Hayfever Plants 

monocotyledons. The flowers are arranged in spikelets of one or several flowers on a 
short and slender axis which is called the rachilla (fig. 15). At the base of the spikelet 
is a pair of scales called the glumes enclosing the structures above them; just above 
the second glume is a similar structure, the lemma, which often has a long slender 
pointed awn growing from its tip. In the axil of the lemma the flower is borne. The 
outer perianth is a two-keeled scale, the palet. The stamens and pistil lie between the 
palet, which is on the inside, and the lemma which is on the outside. The inner perianth 
consists of two tiny scale-like lodicules between the lemma and the ovary. The stamens 
are generally three, occasionally one, two or six. Their anthers are borne on long 
slender filaments which carry them outside of the glumes at maturity. There is one 
pistil with a single ovule but a study of its development shows that it is composed of 
three fused carpels. There are generally two styles or occasionally three. 


FIG. 15. Spikelet of wheat (Triticum), partly diagrammatic. 

The grass family comprises about 4500 species growing anywhere and in any kind 
of soil that is capable of supporting vegetation, and even in water. About 1100 species 
are native or naturalized in North America, and among them are counted some of our 
worst hayfever plants. The pollen of most, if, indeed, not all species appears to be 
capable of sensitizing hayfever patients so that the governing factors in their produc- 
tion of hayfever are primarily their abundance, the amount of pollen set free, and its 
range of dispersal. In these there is an enormous variation among the different species. 
Fortunately, by far the majority of grasses are relatively harmless. Some species 
are wholly or in part self pollinating, the flowers remaining completely closed or only 
opening partly for a short time. Thus some of the panic grasses and rice cutgrass 
(Leersia oryzoides) are self pollinating without opening at all, while the florets of 
wheat expand for a short time, when cross pollination may take place, but for the most 
part are self pollinating. Such cases, however, are not the rule ; the majority are cross 

Chapter III 37 Angiosperms 

pollinated but do not shed enough pollen to be important in hayfever. A relatively 
small number of species account for practically all the grass hayfever. In the eastern 
part of the United States these flower for the most part in the spring or early summer. 
The most important, named in order of their seasonal appearance, are: sweet vernal- 
grass, June grass, orchard grass, appearing in May and early June, and timothy, redtop 
and the various closely related bentgrasses, appearing in June and July. Other species, 
somewhat less important but which frequently contribute their quota of pollen during 
one or the other or both of these periods, are red fescue, meadow fescue, quack grass, 
ryegrass, darnel and velvet grass. Of course there are many others which contribute 
to some degree, but all so much less important that it is rarely necessary to give them 
serious consideration in handling hayfever cases. 

Most of the species already mentioned are grasses of cultivation, consequently are 
widely distributed. In fact they are found wherever the climate is humid and cool. 
In the warm and more arid regions other grasses take their places. Thus Bermuda 
grass extends from coast to coast through the southern states. On account of its wide 
range and long flowering period, lasting throughout the growing season, this is perhaps 
the most important hayfever grass of North America. Frequently associated with 
Bermuda grass in the arid parts of its range is Johnson grass which may be in some 
places almost as troublesome as Bermuda grass, but its distribution is much less ex- 
tensive and its pollen grains are very large, which materially restricts their range 
of dispersal. 

On the Pacific coast ryegrass assumes a position of some importance and in the 
arid and semi-arid regions of the western interior some of the brome grasses. In fact 
each floristic region has its roster of grasses. Still when these are all added up their 
total, though impressive in itself, is small when compared with the 1100 species native 
or naturalized in the United States, or with the 4500 species distributed throughout 
the world. Fortunate, indeed, we are that they are not all to be counted as contributing 
to hayfever. 

Certainly not even all the species enumerated in the following pages are causes 
of hayfever. I have, however, included all that are known to me to have been reported 
in the literature with any justification as causing hayfever or even with hayfever 
possibilities, though I fear that some of them have been reported as the result of exces- 
sive zeal and insufficient study on the part of their discoverers. The relative importance 
or lack of importance of many of these will only become known through further study 
and careful consideration of all the factors concerned, such as the abundance of the 
plants, the amount and character of their pollen. 

The interrelationships of the grasses are somewhat obscure, and even the best 
classifications are admitted to be partly artificial. It seems certain, however, that the 
different genera and species are more closely related to each other than is usual in such 
large families. If other evidence were lacking, this is strongly suggested by the work 
of the allergist, for he finds that a patient who is sensitive to the pollen of one species 
of grass is almost invariably sensitive in some degree to all the grass pollens to which 
he has been exposed, though he may be entirely negative to all pollens except those of 
grasses. Occasionally it appears that a grass hayfever patient may not be sensitive to 
the pollen of species to which he has not been exposed, but in such cases a few years 
exposure is generally all that is necessary to induce sensitization (cf. p. 194, also STULL, 
COOKE and BARNARD 1936 and WALKER 1921). 

For the classification of the grasses of the United States, as now arranged, we are 
all very much indebted to the late Dr. A. S. HITCHCOCK, first, for his "Genera of the 
Grasses of the United States" (HITCHCOCK 1920), secondly, for his Manual of the 
Grasses of the United States (HITCHCOCK 1935). It is this latter work that I follow 
in so far as the taxonomy of the grasses is concerned. 

The family is divided more or less arbitrarily into 14 tribes of which only ten in- 
clude species which are of interest to the student of hayfever. The tribes Batnbuseae, 
Zoysicae, Oryseae and Melinideae are not represented here because they do not include 
plants which can justifiably be considered causes of hayfever. 

Roger P. Wodehouse 38 Hayfever Plants 

Tribe 1. Festuceae 
Bromus (The Brome Grasses) 

The bromes are annual or perennial grasses with terminal open or con- 
tracted panicles of large spikelets. Some of the native perennial species, 
and the introduced European smooth brome, are important forage grasses 
in the mountainous regions of the western United States. The annual 
species are mostly weedy. Some of them are useful range grasses but others 
are serious pests since their barbed fruits work into the eyes, nostrils and 
mouth of stock, causing serious injury. 

Their pollen grains are spheroidal or ovoidal, generally uniform in size, 
about 40 to 48.5/x in diameter, their germ pore 3.4 to 6.3/1, in diameter, and 
with finely granular or faintly reticulate exine (fig. 14). 

The genus comprises about 60 species of which about 36 are native or naturalized 
in the United States. Most of them shed relatively little pollen and are not regarded 
as serious causes of hayfever, though they may occasionally constitute a contributing 
factor in some regions of the western states. 

Smooth or Hungarian brome (B. inennis Leyss.) is a perennial Euro- 
pean species cultivated in America for hay and pasture especially in the 
western states, now running wild almost throughout. It flowers in June 
and July but is not an important factor in hayfever though occasionally 
regarded as such. California brome (B. carinatus Hook. & Arn.) is an 
erect annual or biennial with smooth or slightly hairy leaves and large 
spreading panicles. It is common in open ground, open woods and waste 
places at low and middle altitudes along the Pacific coast, extending into 
British Columbia, Idaho, through Montana to New Mexico. It appears to 
be rather an important cause of hayfever in the Pacific states, in the early 
summer, varying widely in its flowering period in different localities. The 
species merges with the large mountain brorne (B. marginatus Nees) from 
which it can only be distinguished arbitrarily. This latter is an annual or 
short-lived perennial with broader spikelets than in the previous species, 
otherwise similar and to be regarded as a variant of it. 

Chess or cheat (B. secalinus L.), also known as rye-brome and cock- 
grass, is a perennial weed, adventitious from Europe, in grain fields and 
waste places more or less throughout the United States, but it sheds so little 
pollen that it is of little or no importance in hayfever. Soft chess or brome 
(B. mollis L.), also called haver, hooded, bull, lob or lop grass, is an erect 
annual, 8 inches to 3 feet high, softly pubescent throughout. It is a weed, 
adventive from Europe, in waste places almost throughout the United 
States and Canada, except far south. It is particularly abundant on the 
Pacific coast where it is believed to be a contributing factor in hayfever, 
flowering in June and July. In hayfever literature and elsewhere it is fre- 
quently but incorrectly referred to as B. hordeaceus L. 

Ripgut grass (B. rigidus Roth) is a common and troublesome weed, 
and probably an important cause of hayfever in the Pacific coast states, 
especially southern California (RowE 1929), flowering from May to July. 
It is distinguished from the other bromes by its larger awns which some- 
times cause the ripened spikelets to be injurious to stock. 

Chapter III 39 Angiosperms 

Festuca (The Fescues) 

The fescue grasses are low or rather tall, mostly tufted, annuals or 
perennials, with spikelets in narrow or open panicles. Their pollen grains 
are spheroidal, or ovoidal with the germ pore at the large end, 31 to 36.5/x 
in diameter. The pore is approximately circular but with wavy margin, 
2.5 to 4.5ju, in diameter. 

The genus comprises about 100 species, of which about 34 are native or naturalized 
in the United States. Many of the perennial species are important forage grasses in 
the grazing sections of the West and some, such as sheep and red fescue, are cultivated 
as lawn and pasture grasses in the East. Several constitute a serious menace to hay- 
fever sufferers. 

FIG. 16. Meadow fescue (Festuca elatior), flowering stalk. 

Meadow fescue (F. elatior L., F. pratensis Huds., fig. 16), also called 
tall fescue, English bluegrass, Dover grass, Randall or evergreen grass, is 
slender, 2 to 5 feet high, with smooth simple stem and panicle 4 to 14 inches 
long. It is a variable species introduced from Europe and cultivated for 
hay and pasture and naturalized throughout the cooler parts of the United 
States and Canada, in meadows, roadsides and waste places. It flowers in 
June and July and is known to cause hayfever. 

Red fescue (F. rubra L., fig. 17) is a tufted perennial with smooth 
stems rising from creeping rhizomes, \ l /2 to 2 l / 2 feet tall, and panicles 2 to 
5 inches long, sometimes tinged with red. Most of the leaves are basal 
forming a tuft, and are involute filiform, but the few on the stem are short 

Roger P. Wodehouse 


Hayfever Plants 

and flat. It is native of Eurasia but now widely distributed in the cooler 
parts of the northern hemisphere. It flowers principally in June and July 
and is a moderately important cause of hayfever. 

Sheep fescue (F. ovina L.), also called black twitch-grass, is similar to 
red fescue but may be distinguished by its generally more erect habit. It 
appears to be adventive from Europe, but is now widely distributed in 
fields and waste places throughout the United States and Canada, except 
the extreme south. It flowers in June and July and is a contributory cause 
of hayfever. 

FIG. 17. Red fescue (Festuca rubra), flowering stalks. 

Poa (The Bluegrasses) 

The bluegrasses are low or moderately tall slender perennials, or occa- 
sionally annuals, bearing open or contracted panicles, and narrow and 
generally flat leaf blades. Their pollen grains are approximately spheroidal, 
22.5 to 32/i in diameter, with the germ pore more or less irregular in shape, 
and capped by a small operculum which is likewise irregular, and exine 

Chapter III 



rather coarsely granular as compared with that of the pollen grains of other 

The genus comprises about 150 species, widely distributed in all temperate and cold 
regions. About 64 occur naturally in the United States. Nearly all are palatable to 
stock ; some are cultivated for pasture and others form a large part of the forage of 
mountain meadows in the West. Still others are used as lawn grasses. 

One of the commonest species is annual bluegrass, low spear grass, 
dwarf or meadow grass (P. annua L., fig. 18). It is a low tufted, generally 
prostrate grass spreading and rooting at the nodes and often forming mats, 
or occasionally it may assume a more erect form. It is native of Europe 
but naturalized throughout North America, except in the most arid regions, 
in open ground, lawns, pastures, waste places and openings in woods. It 
flowers practically throughout the growing season, in the warmer regions 
even during the winter. In the northeastern states the bulk of its flowering 
takes place very early, usually in April, before that of sweet vernalgrass, 

FIG. 18. Low spear or annual bluegrass (Poa annua). 

and before grass hayfever-cases begin to manifest symptoms. . It is, there- 
fore, safe to say that it is of little importance in hayfever in spite of its 
abundance. This is probably due to the fact that it liberates very little 

Canada bluegrass (P. compressa L.), also called wire grass, flat-stemmed 
meadowgrass and English bluegrass, is a low perennial with slender creeping 
rhizomes and bluish green erect stems, bearing narrow panicles. It is 
naturalized in America from Europe, now widely distributed often in poor 
soil in open grounds, open woods, meadows and waste places throughout 
most of Canada and the northern United States. The plants shed large 
amounts of pollen which is a serious cause of hayfever from June to August. 

June grass, Kentucky bluegrass, or common meadow grass (P. pratensis 
L., fig. 19) is one of the most important hayfever grasses of the United 

Roger P. Wodehouse 


Hayfever Plants 

States. It is a slender perennial, 1 to 3 feet high, from a creeping rhizome, 
with spreading panicles and narrow flat leaves. It is native of Europe but 
thoroughly naturalized in America, and extensively cultivated for lawns 
and pastures in the more humid and northern parts of the United States 
and adjacent Canada. Escaped from cultivation it is distributed almost 
throughout the United States except in the arid regions ; it is not common 
in the Gulf states. It flowers in May and June, at about the same time as 

FIG. 19. June or Kentucky bluegrass (Poa pratensis). 

orchard grass, with which it is often associated, the two together accounting 
for most of the hayfever which occurs during the first half of the grass- 
hayfever season in the East. 

Rough bluegrass or rough-stalked meadow grass (P. trivalis L.) is a 
rough-stemmed perennial, erect from a decumbent base but without creeping 
rhizomes. It is adventive from Europe in the northeastern United States 
and on the Pacific coast in moist places. It may occasionally be an important 
contributing cause of hayfever but in hayfever literature is not generally 
distinguished from Kentucky bluegrass. 

Chapter III 



Saltgrass (Distichlis spicata Greene), also called marsh spike grass 
and alkali grass, is a low perennial from extensively creeping rootstock, 
with rigid stems, rigid convolute leaves and contracted panicles of large, 
smooth, flattened spikelets, the staminate and pistillate flowers borne on 
different plants. Their pollen grains are uniform, spheroidal or ovoidal, 
31 to 34/x, in diameter. 

FIG. 20. Orchard grass (Dactylis glomerata}, three flowering stalks. 

Saltgrass is common in salt and tidal marshes along the Atlantic, Gulf 
and Pacific coasts as far north as Nova Scotia and British Columbia. 
Flowering from June to September, it is believed to be a contributory 
cause of hayfever. 

Orchard grass (Dactylis glomerata L., fig. 20), also called cocksfoot, 
dew or hard grass, is a tall perennial with flat leaves and spreading panicles, 
composed of smaller heads of spikelets, generally forming large tussocks. 
Its pollen grains are spheroidal or ellipsoidal, 28.5 to 38.8/x in diameter. 

Roger P. Wodehouse 44 Hayfever Plants 

Orchard grass is adventive from Europe or Asia, now abundant through- 
out the United States and Canada. It favors moist situations and partial 
shade, hence is frequently used in orchards as a ground cover. It is also 
commonly cultivated as a meadow and pasture grass. As a cause of hay- 
fever it is one of the most important in the United States, shedding its 
pollen in May and June at about the same time as June grass with which 
it is often associated. 

Tribe 2. Hordeae 
Agropyron (The Wheatgrasses) 

The wheatgrasses are perennials, often with creeping rhizomes, and 
usually erect stems and erect green or purplish spikes. Their pollen grains 
are oval, spheroidal or ellipsoidal, about 45 to 52/z in diameter, with exine 
very finely and rather indistinctly granular, the pore approximately cir- 
cular, with smooth margins and small generally excentric operculum, 5.7 
to 8/x in diameter. 

The genus comprises about 50 species, in all temperate regions. About 
23 are native or naturalized in the United States. Most furnish forage and 
a few are among the valuable range grasses of the western states. 

Quackgrass (A. repens Beauv.) is a wiry grass, 1 to 4 feet high, from 
long jointed running rootstocks, with spikes 2 to 8 inches long, narrow 
and flattened. It is naturalized from Europe and now extremely common 
in fields and waste places almost throughout North America except the 
extreme north and is often a troublesome weed. It is known by many 
vernacular names such as quitchgrass, twitchgrass, witchgrass, and couch- 
grass, and locally by other names as stroil, quichens, wickens, and shelly, 
knot, dog, shear, slough and pond grass, bluejoint, false wheat and Colorado 
bluegrass. It flowers from July to September, and is undoubtedly a con- 
tributing factor in hayfever but, in spite of its great abundance and wide 
distribution, it is only of secondary importance because it produces only a 
small amount of pollen. 

Bluestem or western wheatgrass (A. Smithii Rydb.) is a pale green 
glaucous perennial, \ l /2 to 4 feet high, from a slender creeping rootstock. 
It is usually found in moist alkaline soil from Manitoba and Minnesota to 
British Columbia, south to Missouri and Texas. It flowers in June and 
July and is believed to be an important contributory cause of hayfever. 

Wheat (Triticum aestivum L., T. vulgar e Vill., T. sativum Lam.) is a 
low or tall strict grass with flat leaf blades and terminal thick spikes. Its 
pollen grains are irregular in shape but tend to be ovoidal with the germ 
pore at the large end, 48 to 57//, in diameter, the pore generally irregular 
in outline, 6.3 to 9/x in diameter ; the exine finely but distinctly granular. 

Wheat occurs in cultivation in many different varieties, flowering in 
early summer but, though it is perhaps the commonest grass in cultivation, 
it is a negligible cause of hayfever because of its marked tendency to self 

The genus comprises 10 species of southern Europe and western Asia. Of these 
einkorn or one-grained wheat (T. monococcum L.) is sparingly cultivated in Europe 

Chapter III 45 Angiosperms 

and rarely in America. Emmer (T. dicoccum Schrank) is occasionally cultivated in 
America as a forage plant. For a further discussion and bibliography of the wheats 
the reader is referred to HITCHCOCK (1920, 1935), for a classification of the varieties 
grown in the United States to CLARK and BAYLES (1935). 

Hordeum (Barley) 

The barleys comprise about 20 species widely distributed in both hemi- 
spheres. Besides the cultivated barley, which appears to be harmless in 
hayfever, there are about 7 species found growing wild in the United 
States, some of them weeds with hayfever possibilities. Foxtail barley 
(H. jubatum L.) is a perennial tufted grass with decumbent base and nod- 
ding spikes. It occurs in open ground, meadows and waste places almost 
throughout the United States, except the southern states, and is a trouble- 
some weed believed to have hayfever possibilities in the western states. 
Mouse barley (H. murinum L.) also called wall barley, way bent, squirrel 
tail, barley grass, foxtail and wild barley, is a similar plant, adventive from 
Europe, common on the Pacific coast, Idaho and British Columbia, south 
to Utah, New Mexico and California. Neither sheds enough pollen to be 
important in hayfever. 

Lolium (Ryegrass) 

The ryegrasses are annuals or perennials with flat leaf blades and ter- 
minal spikes. Their pollen grains are spheroidal or ovoidal with the germ 
pore at the large end, 30 to 37.6/x in diameter, the pore approximately circu- 
lar, 2.8 to 5/x, in diameter, with a relatively small operculum, and the exine 
faintly granular or reticulate. 

The genus comprises about six species, native of the Old World, mostly valuable 
meadow grasses. Four of these have been introduced into the United States for use 
as meadow and lawn grasses. 

Perennial ryegrass or ray grass (L. perenne L., fig. 21), also called red 
ray, ever grass, red darnel, red dare, English bluegrass, and English rye- 
grass, is a short-lived perennial, erect or decumbent at the base, y 2 to 2 l / 2 
feet tall, with slender arching flattened spikes. It is cultivated in meadows, 
pastures and lawns, and escaped in waste places almost throughout North 
America, except far south. It flowers in July and August shedding large 
amounts of pollen which is a serious cause of hayfever in some regions. It 
has even been stated by SELFRIDGE ( 1920) to be "The most important hay- 
fever producer of all the grass family on the Pacific Coast". 

Italian ryegrass (L. multiflorum Lam., L. italicum A. Br.), also called 
rye grass or wintergrass, is similar in most respects to perennial ryegrass, 
except that its pollen grains are slightly larger, about 37.5/x in diameter, and 
is of similar distribution. It flowers from June to August, and is moderately 
important in hayfever. 

Darnel (L. temulentum L.), also called poison or bearded darnel, or 
Ivray is an annual, 2 to 4 feet high, erect, simple and smooth. Its pollen 
grains are various, spheroidal, ovoidal or ellipsoidal, 29.5 to 37.6ju in diame- 

Roger P. Wodehouse 


Hayfever Plants 

ter, with pore 4 to 5. I/A in diameter, and exine finely granular. It is occa- 
sionally found as a weed in waste places and cultivated fields almost through- 
out the region east of the Mississippi River, and on the Pacific coast. 
Flowering from June to August, it appears to be a contributory factor 
in hayfever. 

Rye (Secale cereale L.) is a tall annual grass with flat leaves and simple 
stems. Its pollen grains are ellipsoidal, 53 to 57/x long and 38 to 43.5ju 
broad, with the germ pore on the side and towards one end, about 5.7/x in 

FIG. 21. Perennial ryegrass (Lolium perennc), flowering stalks. 

diameter, circular with a relatively small operculum. This is one of the 
few kinds of grass pollen grains that can always be readily identified ; its 
large size together with its ellipsoidal form and one-sided placement of 
the pore are distinctive for this species. Rye is more commonly cultivated 
in Europe than in America, but here it is frequently escaped in fields and 
waste places. It is not native of America, probably coming originally from 
southern Asia. It flowers from May to June shedding prodigious quantities 
of pollen which is undoubtedly the cause of some hayfever, especially in 
Europe. The large size of its pollen grains, however, greatly restricts its 
effective range. 

Chapter III 47 Angiosperms 

Tribe 3. Aveneae 
Avena (The Oats) 

The oats are annual or perennial with usually flat leaves and terminal 
panicles. The genus comprises about 50 species, widely distributed in 
temperate regions, chiefly in the Old World. Several species and hybrid 
varieties are cultivated for hay and grain. Their pollen grains are generally 
ovoidal with the germ pore at the large end, 54 to 62/x long, the pore circular 
or slightly irregular in outline, 4 to 8ju in diameter, its operculum about half 
as broad. The exine is distinctly and rather coarsely granular. 

Wild oat (A. fatua L.) is an erect glabrous annual, 1 to 4 feet tall, with 

FIG. 22. Velvet grass (Holcus lanatus), flowering stalks. 

large and loose panicles of mostly three-flowered spikelets. It is adventive 
from Europe in fields and waste places in the United States, rare in the 
East but abundant on the Pacific coast where it is regarded as an important 
cause of hayfever, flowering from July to September. Slender wild oat 
(A. barbata Brot.) is a similar species but more slender and with mostly 
two-flowered spikelets. It is a common weed of the Pacific coast states and 
Arizona where it is regarded as a contributory cause of hayfever. The culti- 
vated oat (A. sativa L.) is a glabrous annual, about 3 feet high, differing 
from A. jatua in having smaller and two-flowered spikelets. It is cultivated 
in every state and much of Canada, but more especially in the north central 

Roger P. Wodehouse 48 Hayfever Plants 

states or "corn belt", but it is not a factor in hayfever because it is generally 
self pollinated. For a discussion of the different varieties of oat in culti- 
vation see ST ANTON (1929). 

Velvet grass (Holcus lanatus L., Nothoholcus lanatus Nash, fig. 22) is 
grayish velvety pubescent, l l / 2 to 3 feet tall, erect, or decumbent at the base. 
Its pollen grains are spheroidal, 29.5 to 34/i in diameter, the pore circular 
or irregular, about 3.4/x in diameter, the exine very faintly and finely granu- 
lar. The grass is adventitious from Europe, occasionally cultivated on 
light sandy soil in fields, meadows, and waste places almost throughout the 
United States east of the Mississippi River, except far south, and on the 
Pacific coast. It flowers from June to August and is a contributing factor 
in hayfever in regions where abundant, and is said to be important in Cali- 
fornia and Oregon. It is called by various names in different places, such 
as meadow or woolly soft-grass, velvet mesquite, old whitetop, feather grass, 
and in England, where it is an important cause of hayfever, is known as 
Yorkshire fog. 

Wild oatgrass or poverty oatgrass (Danthonia spicta Beauv., Avcna 
spicata L.) is a tufted erect perennial, 1 to 2y 2 feet tall, with narrow 
leaves and small terminal panicles. Its pollen grains are spheroidal, 28 to 
35/x in diameter, the pore circular, about 5.2/A in diameter and with a small 
generally irregularly shaped operculum, and exine finely but distinctly 
reticulate granular. 

It occurs in dry soil almost throughout the United States and adjacent Canada, 
except the arid Southwest. It flowers from July to September but is not believed to be 
important in hayfever. 

The genus comprises about 100 species of warm and temperate regions, principally 
of South Africa. 

Western June grass (Koeleria cristata Pers., K. gracilis Pers.), also 
known as Koeler's grass, crested hair grass and prairie June grass, is a 
slender, low or moderately tall cespitose perennial with narrow leaves and 
shining spike-like panicles. Its pollen grains are spheroidal, 27.4 to 28/x in 
diameter, the pore generally irregular in form, about 3.4ju, in diameter, exine 
finely granular. This species occurs on prairies, in open woods and sandy 
soil almost throughout the United States and adjacent parts of Canada and 
Mexico, except the southeastern states, also in Europe. It flowers from 
July to September, and is said to be an important cause of hayfever in the 
western part of its range, e.g., Oregon (CHAMBERLAIN 1927) and Wyoming 


The genus comprises about 20 species in the temperate regions of both hemi- 
spheres. K. cristata is the only one native to the United States. K. phleoides Pers., a 
small annual species has been introduced from Europe and is found sparingly in a few 
localities on the Atlantic and Pacific coasts. 

Tribe 4. Agrostideae 

Meadow foxtail (Alopecurus pratensis L.) is an erect perennial, 2 to 
3 feet tall, with compact spikes, 2 to 4 inches long and about J4 ulc h thick, 
resembling timothy. This species was introduced into America from 
Europe as a meadow grass. It is now rather widely distributed in the 

Chapter III 



northeastern United States and Canada and in Oregon, but not generally 
abundant. It flowers from May to June and is probably a contributory 
cause of hayfever in the few regions where it is abundant, possibly in Massa- 
chusetts. It may be distinguished from timothy by its habit of flowering 
several weeks earlier. 

FIG. 23. Timothy (Phleum pratensc}, three flowering stalks. 

Timothy (Phleum pratensc L., fig. 23) or Herd's grass is an erect short- 
lived perennial, 2 to 4 feet tall, with elongate compact inflorescence several 
times longer than broad. Its pollen grains (fig. 14 A, D) are spheroidal, 
32 to 36.5ji in diameter, the pore circular or somewhat irregular, 1.7 to 2.8/x 
in diameter, and its operculum very irregular, sometimes fragmentary, the 
exine finely but distinctly granular. 

Roger P. Wodehouse 


Hayfever Plants 

Timothy is native of Europe and northern Asia, commonly cultivated in 
America and Europe. It is the most important meadow grass in America, 
and is found escaped in fields and waste places throughout the United States. 
"The region of the United States most favorable to the growth of timothy 
.... is the cool humid region which includes the northeastern portion west 

FIG. 24. Redtop (Agrostis alba}, flowering stalks. 

to the Great Plains and south to Virginia and Missouri, also on the Pacific 
coast from northern California to Puget Sound". It flowers during June 
and July, shedding enormous quantities of pollen which is one of the worst 
causes of hayfever in the early summer. 

The genus comprises 10 species in temperate regions of both hemispheres. Four 
are found in the United States, but of these only mountain timothy (P. alpinum L.) 
is native. 

Chapter III 51 Angiosperms 

Redtop or Herd's grass (Agrostis alba L., fig. 24), also called whitetop 
or creeping bent grass, is erect, or decumbent at the base, 2 to 4 feet high 
from creeping perennial rhizomes, with open, usually reddish panicles. Its 
pollen grains are spheroidal, 26 to 31.2/* in diameter, their pore approxi- 
mately circular, 2.3 to 4.6/x in diameter, with a small generally irregularly 
shaped operculum, the exine finely but conspicuously granular. "Redtop 
is cultivated as a meadow and pasture grass in the northern United States 
and Canada, especially upon acid soils and those too wet for timothy". It 
is naturalized from Europe but is now established almost throughout North 
America. It flowers from June to July at about the same time as timothy 
shedding prodigious quantities of pollen which together with that of timothy 
causes most of the hayfever occurring during the second half of the grass 
hayfever season in the East. 

The genus comprises about 100 species distributed throughout the world, 
especially in temperate regions. Thirty-two, mostly adventive species from 
Europe, are found in the United States. Most of them are valuable forage 
plants; colonial bent (A. tennis Sibth.) is used for pastures, lawns and golf 
courses; creeping bent (A. palustris Huds.), velvet bent (A. canina L.), 
and Washington bent and metropolitan bent, which are forms of A. palus- 
tris, are coming into use for lawns and golf greens. These and other species 
of bent grass appear to be allergically indistinguishable from each other or 
from redtop. All flower in the early part of summer shedding large quanti- 
ties of exceptionally buoyant pollen which is the cause of much hayfever. 

American beachgrass (Ammophila breviligulata Fern.), also called sea-sand reed, 
sea-mat weed, marram grass, sea marram, is a tough coarse perennial with hard scaly 
creeping rhizomes, long, tough involute blades, and dense spike-like panicles. Its 
pollen grains are spheroidal, ellipsoidal or ovoidal, 34 to 39/A in diameter ; pores nearly 
circular, about 3.4^ in diameter, with a small irregularly shaped operculum which is 
even sometimes fragmentary. The American beachgrass is an important sand binder 
extensively used to arrest drifting sand dunes on Cape Cod and along the Atlantic coast 
from North Carolina to Newfoundland, also along the shores of the Great Lakes. On 
the Pacific coast, possibly also partly along the Atlantic, its place is taken by the very 
similar European beachgrass (A. arenaria Link) which has also been successfully used 
as a sand binder. Both species flower late in summer, June to September, shedding 
rather large amounts of pollen which probably contributes locally to hayfever. 

Tribe 5. Ghlorideae 

Bermuda grass (Cynodon Dactylon Pers., Capriola Dactylon Ktze., 
fig. 25), also called scutch grass, wire grass, Bahama grass, is a low peren- 
nial with creeping rhizomes, short leaf blades and several slender digitate 
spikes at the summit of the upright flowering stems. Its pollen grains are 
spheroidal, 34 to 35.5/x in diameter, with rather coarsely granular exine. 

Bermuda grass is widely distributed in the southern states from coast 
to coast, where it is used as a lawn and pasture grass and in some places cut 
for hay. It is particularly abundant in the irrigated regions of the arid 
Southwest and is a troublesome weed in much of the semiarid region. It 
flowers almost throughout the growing season which, in the warmer parts 
of its range, extends over a period of eleven months. As a consequence 
of its extraordinary abundance and wide distribution, and the copiousness 

Roger P. Wodehouse 


Hayfever Plants 

and buoyant nature of its pollen, it is perhaps the worst hayfever grass in 
the United States. It is stated by some authors to be native of the Bengal 
region of India, by others of southern Europe or the Mediterranean region. 
At any rate it is "Common in open rather dry ground in the warmer parts 
of both hemispheres, apparently introduced into America" (HITCHCOCK 
1936). From whence or when it came to America seems to be uncertain, 



I /> 


FIG. 25. Bermuda grass (Cynodon Dactylon). 

but THOMMEN (1931) states that, "as early as 1807 it was described by 
JAMES MEASE in his Geological Account of the United States, as follows : 
'probably as important a grass as any in the southern states is Bermuda 
grass, which grows with great luxuriance and propagates with astonishing 
rapidity by means of its numerous jointings, every one of which takes root' ". 

Chapter III 53 Angiosperms 

A larger form which is found along the coast of Florida has been called 
Cynodon maritinms H.B.K. but appears to be only a form of C. Dactylon. 
Three other species are included in this genus but these occur only in 

Bouteloua (The Gramas) 

The gramas are perennial, or sometimes annual, stoloniferous or cespi- 
tose grasses with several to many spikes arranged in unilateral racemes. 
The genus comprises about 38 species, chiefly North American, 18 in the 
United States, and these constitute one of the most important groups of 
native pasture grasses in the northern prairie region forming a large part 
of the "buffalo-grass formation," originally covering thousands of square 
miles. In distribution the genus extends from Saskatchewan and Manitoba 
southward between the Mississippi River and the Continental Divide. The 
western border crosses the Divide in Wyoming and extends into the south- 
ern Great Basin region and strikes the Pacific coast at about the Mexican 
border (GRIFFITHS 1912). 

Several species are mentioned in hayfever literature as possible causes 
of hayfever, but they are all modest pollen shedders and not likely to be of 
much importance. Indeed the destruction of these grasses and their replace- 
ment by various kinds of weeds is responsible for much hayfever. 

Blue grama (B. gracilis Lag., B. oligostachya Torn), also called mesquite or 
buffalo grass, is a tufted perennial with numerous short leaves and two or three one- 
sided spikes about an inch long, one at the top and the other one or two a short distance 
down the stem. Its pollen grains are spheroidal, 34.2 to 38/i in diameter, with an ir- 
regularly shaped germ pore, 3.4 to 3.7^ in diameter, and exine of finely and faintly 
granular texture. 

This species is found in the Great Plains from Manitoba to Mexico and southward 
to South America. Along with buffalo grass it constitutes most of what is known in 
the Middle West as "Short Grass". It flowers from July to September and in places 
where still abundant may be a contributory cause of hayfever of slight importance. 
Other common species are hairy or black grama (B. hirsuta Lag.) of about the same 
distribution as B. gracilis and similar in appearance; side-oats grama (B. curtipendula 
Torn), the tallest species sometimes reaching 3 ft. and further distinguished by its 
numerous reflexed spikelets, in its range extending further east, even reaching Connecti- 
cut; black grama or woollyfoot (B. eriopoda Torr.), a low creeping species of Arizona 
and New Mexico; Rothrock grama (B. Rothrockii Vasey) which is the most important 
range grass in many parts of Arizona ; sixweeks grama, which really includes at least 
two species, B. barbata Lag., a low tufted annual, and B. Parry i Griffiths, an annual 
resembling Rothrock grama, both of the Southwest. In hayfever studies distinction 
is seldom made between the different species. 

Buffalo grass (Buchloe dactyloidcs Engelm., Bulbilis dactyloides Raf.) 
is also closely related to the gramas, and often associated with them. It 
is a low stoloniferous gray-green perennial with curly leaf blades, forming 
dense sods. It is dioecious, the staminate culms slender, 2 to 8 inches high, 
the pistillate spikelets mostly 4 or 5 in a short spike. This is one of the 
most important native American grazing grasses of the dry plains region 
from Canada to Mexico between the Mississippi River and the Continental 
Divide, and in New Mexico and Arizona. "It is dominant over large areas 
on the uplands of the Great Plains, colloquially known as 'short grass 

Roger P. Wodehouse 


Hayfever Plants 

country'. . . . The sod houses of the early settlers were made mostly from 
the sod of this grass" (HITCHCOCK 1935). It grows on both heavy and 
sandy soils and before its widespread destruction through agriculture was 
important in holding such soils against wind erosion. It flowers in June 
and July but appears to be unimportant in hayfever. This and blue grama 
have recently been shown by SAVAGE (1935) to possess the highest resist- 
ance to drought of any native American grasses. 

Saltmeadow cordgrass (Spartina patens Muhl.) is a common grass of salt marshes 
and sandy meadows along the coast from Quebec to Florida and Texas, and in saline 
marshes inland, New York and Michigan. It often forms compact masses in pure 
stands along the Atlantic coast where it is cut for marsh hay. It flowers in August 
and has been suspected of causing some hayfever. Though it is only a moderate pollen 
shedder it grows in such abundance in some places that it seems possible that it may 
occasionally be a minor cause of late summer hayfever. 

The genus of cord grasses comprises about 7 species widely distributed in salt 
marshes and are important soil builders in coastal and interior marshes. Apparently, 
however, none is important in hayfever. 

FIG. 26. Sweet vernalgrass (Anthoxanthum odoratum). 

Chapter III 55 Angiosperms 

Tribe 6. Phalarideae 

Sweet vernalgrass (Anthoxanthum odoratum L., fig. 26) is a fragrant 
perennial with flattened leaves and spike-like panicles. Its pollen grains are 
spheroidal, 37.5 to 45.6/x in diameter, the germ pore variously irregular, 
4 to 6.3/x in diameter and with a small and irregularly shaped operculum, 
the exine of a faintly granular texture. It is a common weed introduced 
from Europe in fields, meadows and along roadsides almost throughout the 
eastern part of Canada and the United States east of the Mississippi River, 
and on the Pacific coast from northern California northward. In the north- 
eastern part of the United States this is the first important grass to flower 
in the spring, following closely annual bluegrass, about the first week in 
May, and continuing until the end of June. It is unquestionably one of the 
most important hayfever grasses throughout a large part of its range. 

The genus comprises four species native of Europe and Asia, of which 
only the present species has become established in the United States. 

Mediterranean canary grass (Phalaris minor Retz.) is an annual \ l / 2 to 2^ feet 
high, with broad leaves and short spikes or almost capitate inflorescence. Its pollen 
grains are spheroidal, 36.5 to 38.5/* in diameter, the pore approximately circular, 3.2 
to 4.6> in diameter, with a small and irregularly shaped operculum, and exine of faintly 
granular texture. This grass was introduced from Europe, and now occurs sparingly 
in Louisiana and Texas, but more abundantly in California where it flowers in August 
and has occasionally been suspected of causing hayfever, though it sheds too little pollen 
to be of much importance. 

The genus comprises 10 species, native of southern Europe and the southern United 
States. Reed canary grass (P. anmdinacea L.) is native of North America and is 
cultivated in the Pacific coast sections of Washington and northern California for hay 
and pasture. Canary grass (P. canariensis L.), a source of canary seed, is introduced 
from the Mediterranean region throughout most of the United States but is seldom 
abundant. None of the species can be regarded as important in hayfever though some 
are occasionally mentioned in the literature. 

Tribe 7. Zizaneae 

Indian rice, wildrice or water oats (Zizanea aquatica L., Z. palustris L.) 
is a tall graceful aquatic annual with long flat leaves and a large terminal 
panicle bearing pistillate flowers on its upper branches and staminate on 
the lower. Its pollen grains are spheroidal, 34.2 to 40/x in diameter, with 
the pore circular, about 4.5/i in diameter, and a small and irregularly shaped 
operculum. This grass is abundant in swamps and slow streams throughout 
the eastern half of the United States and Canada. It flowers from June 
almost to the end of summer, producing a fairly large amount of pollen, 
but appears to be unimportant in hayfever. 

The genus comprises only two other species ; one Z. texana Hitchc., is similar in 
appearance but perennial, native of Texas, the other native of eastern Asia. 

Tribe 8. Paniceae 

Natal grass (Tricholaena rosea Nees) is an annual or short-lived peren- 
nial, tall, slender and upright, with beautiful fuzzy purple panicles, 4 to 10 
inches long. Its pollen grains are uniform, spheroidal, 34.5 to 41.5/t in 
diameter, with a germ pore 4 to 4.6/tz in diameter, its operculum about 3.4//. 

Roger P. Wodehouse 56 Hayfever Plants 

in diameter both nearly circular, and with exine finely and faintly granular. 
This grass is adventive from South Africa and cultivated as a meadow grass 
on sandy soils in Florida and to a lesser extent along the Gulf coast. It is 
sometimes used as a ground cover in citrus groves in Florida, and in many 
places has assumed the status of a weed along roadsides, grasslands and 
sandy fields, often so completely occupying these as to turn large sweeps of 
land a brilliant purple with its beautifully colored panicles. It is, however, 
only a sparse pollen shedder and, though its role in hayfever is not fully 
understood, there is no concrete evidence to suggest that it is more than a 
minor and local contributor to hayfever. 

Crabgrass (Digitaria sanguinalis Scop., Syntherisma sanguinalis Dulac), 
also called hairy finger grass, crowfoot or pigeon grass, is an erect or decum- 
bent annual often rooting at the lower nodes, 1 to 3 feet high, with flowers 
in 3 to 10 racemes digitate at the top of the stem, appearing late in August 
and September. Its pollen grains are spheroidal, 32 to 39/x in diameter, the 
pore approximately circular, 3.4 to 4.6ft in diameter with a small irregularly 
shaped operculum, and the exine coarsely and distinctly granular. This 
grass bears a strong superficial resemblance to Bermuda grass, and is some- 
times mistaken for it by students of hayfever. The two may readily be told 
apart, however, by simply pulling them up ; crabgrass is annual with fibrous 
roots, whereas Bermuda grass is perennial with an extensively creeping 
rhizome. Moreover crabgrass is generally much larger and coarser than 
Bermuda grass, and is tinged more or less with purple, especially as it 
grows old. It is native of Europe, but now a troublesome weed in waste 
places and cultivated ground almost throughout the United States. It does 
not produce enough pollen to be of any importance in hayfever in spite of 
the great abundance of the plants. 

St. Augustine or short grass (Stenotaphrum sccundatum Ktze.), also called run- 
ning crabgrass, is a low creeping stoloniferous perennial with short flowering stalks, 
distinguished by their thick corky rachis in which the spikelets are imbedded along one 
side. It occurs in moist, especially mucky, soil, near the sea shore, from South Caro- 
lina to Texas. It is native of the southern states and tropical America, and is common 
in the West Indies and Bermuda. It is one of the best grasses for forming lawns in 
warm tropical climates, and is much used for that purpose in the Gulf coastal towns, 
particularly in Florida. It flowers almost continuously and has been suspected of 
causing hayfever, but it is unlikely to be a factor of importance. 

Paspalum (The Paspalum or Bull Grasses) 

Paspalum is a genus of over 300 species widely distributed in the warmer 
parts of both hemispheres. Of these about 42 are native or naturalized in 
the United States and two appear to have hayfever possibilities. Dallis 
grass (P. dilatatum Poir.), also called water grass and tall bull grass, is a 
tall perennial, 2 to 4 feet high, with erect stems, leafy at the base bearing a 
lax panicle of three to five spreading racemes of spikelets arranged in twos 
on the outer side of a dilated rachis, and fringed with long silky white hairs. 
It is native of South America, recently introduced into the United States 
and cultivated as a pasture grass in the southeastern states. It now occurs 
in low ground from rather dry prairie condition to marshy meadows, from 

Chapter III 



New Jersey to Tennessee and Florida west to Arkansas and Texas. It 
flowers from early spring to late fall, and is believed to be a contributory 
cause of hayfever. PENFOUND, EFRON and MORRISON (1930) point out 
that it is one of the most abundant grasses in the vicinity of New Orleans, 
rating it second to June grass. 

Vasey grass (P. Urvillei Steud., P. Vaseyanum Scribn.), also called hairy bull 
grass, is similar to Dallis grass but with a larger and more compact panicle of 10 to 
20 racemes. It also comes from South America, introduced from Argentina as a 
pasture grass in the southeastern states. It is now escaped and found in fields and low 
places in the coastal plane area from Florida to Texas, and South Carolina. Its role 
in hayfever is not fully understood, but there seem to be grounds for supposing that it 
has hayfever possibilities. 

FIG. 27. Johnson grass (Sorghum halepense). 

Roger P. Wodehouse 58 Hayfever Plants 

Tribe 9. Andropogoneae 

The sorghums are mostly tall annuals or perennials with long flat leaves 
and large terminal panicles. Their pollen grains are spheroidal, large, 40 to 
57/x in diameter, with a circular or somewhat irregularly shaped germ pore, 
3.4 to 5.1/x in diameter, with a large operculum also generally somewhat 
irregular in shape and excentrically placed on the pore membrane, the exine 
finely and distinctly granular. There appears to be no difference between 
the pollen grains of the several species and their numerous varieties which 
are encountered in hayfever studies. The genus comprises about 10 species, 
widely distributed in temperate and tropical regions. Of these only the 
following two have been introduced into America. 

Johnson grass (Sorghum halepense Pers., Holcus halepensis L., Andro- 
pogon halepensis Brot., fig. 27), also called evergreen or Egyptian millet, 
is an erect perennial with extensively creeping rootstock, 3 to 5 feet tall, 
simple or sometimes branched, smooth, with open panicle, y* to \ l /2 feet 
long. This grass was introduced into the United States from the Mediter- 
ranean region as a forage plant in the arid regions on account of its drought- 
resisting qualities, but it has escaped and spread throughout most of the 
warmer part of the United States, extending from New Jersey and Penn- 
sylvania to Iowa and Kansas, south to Florida and Texas, and west to 
southern California, and now is a common weed in open ground, fields and 
waste places. It flowers from July to September, and throughout its effec- 
tive range which almost coincides with that of Bermuda grass, is believed 
to be the cause of much hayfever. 

Sorghum (Sorghum vulgar c Pers., Holcus Sorghum L., Andropogon Sorghum 
Brot.) is similar to Johnson grass, but annual and generally larger. It originated in 
Africa but has been cultivated since pre-historic times. Like most plants old in cultiva- 
tion, it occurs in many varieties differing widely in appearance and the uses to which 
they may be put. Of those which have reached America, some have received varietal 
names, and some are even regarded as distinct species, but most are poorly defined 
and perhaps inconstant. Many of them produce sufficient pollen to cause them to be 
worthy of consideration in hayfever studies, but there is no need to differentiate between 
the varieties. The sorghums are cultivated in America chiefly in the regions from 
Kansas and Texas to North Carolina, for forage and for the juice which is made into 
syrup. They have not become established as Johnson grass has, and scarcely sustain 
themselves outside of cultivation. They flower late in summer, for the most part from 
July to September. Sudan grass (var. sudanensis Hitchc.) is similar to Johnson grass, 
except for its annual habit and greater height. It is extensively grown for hay and 
pasture. This is perhaps the most distinct variety, and is even sometimes regarded as 
a distinct species going by such names as Sorghum sudanensis Stapf and Holcus suda- 
nensis Bailey. Other varieties encountered in American literature are Kafir, Shallu, 
Durra, Broomcorn and Sorgho. 

Tribe 10. Tripsaceae 

Maize or Indian corn (Zea Mays L.) is a robust monoecious annual, 
3 to 12 feet high, unbranched but often with prop roots springing from the 
lower nodes. The staminate flowers are borne in long spike-like racemes 
forming a large spreading terminal panicle, the "tassel", the pistillate 

Chapter III 59 Angiosperms 

flowers borne in the ears in the axils of the lower leaves, their greatly 
elongate styles forming the "silk". The pollen grains are approximately 
spherical, 80 to 100/u in diameter, the pore circular, 6.8 to 9.1/t in diameter, 
its operculum very irregular, 2.3 to 3.4/x in diameter, frequently represented 
by an aggregation of more or less distinct fragments on the pore membrane. 
The texture of the exine is finely but distinctly granular. This is apparently 
the largest of all the grass pollen grains. 

Maize is one of the most important economic plants of the world. It 
is cultivated throughout the United States and most of Canada. Its pollen 
is known to be toxic to hayfever patients and is at times a cause of hayfever, 
but the large size of the grains prevents it from becoming atmospheric in 
the sense that that of ragweed and most of the hayfever grasses is. The 
genus comprises only this species, though occurring in many varieties. It 
is known only in cultivation, appearing to have originated among the 
American aborigines on the Mexican plateau in prehistoric times. 

Gyperaceae (The Family of the Sedges and Spike-rushes) 

These are grass-like or rush-like herbs, with slender solid stems, gen- 
erally angular, rarely cylindrical, and narrow leaves similar to those of the 
grasses but with generally closed sheaths. Their flowers are inconspicuous 
and greenish or brownish arranged in spikelets, adapted to wind pollination. 

The family comprises about 75 genera and more than 3000 species of mostly marsh 
or aquatic herbs. Many species shed enormous quantities of extremely buoyant pollen, 
which is caught on pollen slides in considerable abundance throughout most of the 
summer. Nevertheless they appear to be of little if any importance in hayfever, though 
several have been recorded as possible causes. To this family belong the papyrus of 
Egypt (Papyrus antiquorum), the umbrella plant (Cyperus alterniflorum) , also a 
native of Africa now a common pot or porch plant, the spike-rushes (Eleocharis) and 
the true bull rushes which are species of the genus Scirpus. 

Carex (The Sedges) 

The sedges are perennial grass-like herbs with three-angled stems and 
three ranked leaves, monoecious or dioecious with inconspicuous greenish 
flowers. The pollen grains (fig. 14C) of the two following species are 
pear shaped, about 38/x broad, with a single irregularly shaped and poorly 
defined germ pore at the large end, and thin exine of granular texture, and 
irregularly thickened intine with deep inward protrusions on the sides of 
the grain. When dry the grain is polyhedral, generally tetrahedral. 

The genus comprises over 1000 species widely distributed, most abundant in tem- 
perate zones, many of them common in bogs and moist places, a few in light dry sandy 
soil. Some of them shed much pollen which has been occasionally suspected of causing 
hayfever (ELLIS and ROSENDAHL 1933). Tussock sedge (C. stricta Lam.) is a tall 
smooth and dark green perennial generally growing in dense clumps, abundant in 
swamps throughout the eastern half of the United States and Canada. It flowers in 
April and May, shedding much pollen which is frequently caught on atmospheric pollen 
slides. Carex Pennsylvania Lam. is a low grass-like herb with creeping stolons, abun- 
dant in dry soil throughout the northeastern part of the United States and Canada. It 
flowers from April to June, when its pollen may be caught on atmospheric pollen 

Roger P. Wodehouse 60 Hayfever Plants 

Nutgrass (Cyperus esculentus L.) also called galingale, chufa and nutrush, though 
it is neither a grass nor a rush. It is a low tufted sedge with extensive slender root- 
stocks bearing edible nut-like tubers. It is a pernicious weed of gardens, along paths 
and sidewalks, and along streams especially in sandy soil. It is native of Europe but 
completely established in the United States from Virginia to Florida and westward to 
Texas, sparingly elsewhere. It has occasionally been suspected of causing hayfever 
though this has not been demonstrated. Since it has the characteristics of a hayfever 
plant in its abundance and the buoyant nature of its pollen it deserves further investiga- 
tion in regions where abundant. 

Juncaceae (The Family of the True Rushes) 

The rushes are grass-like usually tufted herbs with flat or round leaves, 
generally with compound inflorescence, and the flowers scattered along the 
branches, or in dense heads, their perianth inconspicuous, whitish, greenish, 
yellowish or brownish, consisting of three chaffy sepals and three chaffy 
petals. In their floral structure the rushes are thus much less reduced or 
divergent from the general monocotyledonous form than the grasses, but 
like the grasses they are entirely wind pollinated. The family comprises 
about 300 species in 8 genera, of wide distribution, two of the genera repre- 
sented in North America. Rush pollen is frequently caught on atmospheric 
pollen slides, but is not known to cause hayfever. All those which I have 
examined shed pollen only sparingly. 

The common wood rush (Juncoides campestre Ktze., Luzula campestris 
DC.) is a low herb with densely tufted stems, 4 to 20 inches high, bearing 
2 to 4 leaves, their blades flat and tapering to a gland-like blunt point, 
sparingly webbed when young. The pollen grains of the wood rush (fig. 
31 A) are uniform in shape and size, always united in groups of four tetra- 
hedrally arranged, the four grains of each tetrad so closely appressed that 
the group is almost spherical. The individual cells are 21.1 to 29.6/x in 
diameter. The exine is thin and flecked with small granules, and continuous 
from grain to grain over the whole tetrad, but the sutures between the 
adjoining grains are plainly visible through the exine. The intine is thick 
and hyaline, thicker on the walls of the dissepiments than on the outside 
walls. Each cell is provided with a single germinal area of thinner exine 
on its distal side and not sharply marked off from the rest of the exine. 

The wood rush is common in woodlands almost throughout North 
America, also in Europe and Asia. It flowers very early in spring. Though 
wind pollinated its pollen is rarely caught on pollen slides, and does not 
cause hayfever. 


The dicotyledons are the flowering plants which generally have obvi- 
ously two seed leaves or cotyledons ; occasionally, however, one or both 
may remain in the seed. The first foliage leaves are generally opposite. The 
stems are formed of bast, wood and pith, and may be increased in thickness 
by the annual addition of layers of wood and bast generated by a growing 
layer of cambium between them. The parts of the flower are seldom in 
threes, frequently in fours or fives. 

Chapter III 61 Angiosperms 

The dicotyledons include about ^ of the living flowering plants. Here 
belong all the angiospermous trees and shrubs, except such monocotyledons 
as some liliads, Pandanales, bamboos and palms. They can generally be 
distinguished by a cross section of their stem which shows the vascular 
tissue in an unbroken cylinder about the pith in the center or, if in separate 
bundles as in herbaceous or young woody stems, the bundles arranged in 
a ring. 

Salicaceae (The Willows and Poplars) 

The Salicaceae are trees or shrubs with simple alternate stipulate leaves, 
and dioecious flowers in catkins, appearing before or at the same time as the 
leaves, both male and female without perianth, borne in the axils of bracts. 

The family comprises but two genera, the willows (Salix) and the 
poplars (Populus), mainly of the north temperate zone. The willows are 
primarily insect pollinated, but are certainly also wind pollinated to a 
certain extent. Their flowers which are borne in upright catkins (fig. 28), 
are conspicuously colored, sweet scented and provided with nectar which 
is secreted by a small scale at the base of each flower, and they succeed in 
attracting to themselves large numbers of bees. On the other hand the 
stamens protrude so that the pollen which is only slightly sticky is easily 
scattered in the air, and is often caught on atmospheric pollen slides several 
miles from the trees. The ability to secure pollination through the agency 
of either insects or wind probably explains the enormous latitudinal range 
and the variety of habitats occupied by the willows. The genus comprises 
500 or more species ranging throughout north temperate and arctic regions. 
The arctic willow (S. polaris) reaches the extreme northern limit of vegeta- 
tion ; it has been found in flower and bearing seed on the northernmost tip 
of Greenland. Here the plants even when many years old have stems no 
thicker than the finger, which lie flat on the ground forming by their pro- 
fuse branching a network through which the leaves and catkins peep out 
(THOROLD WULFF in RASMUSSEN 1916 Thule Expedition). A few species 
also occur in the West Indies and Central America and southward to 
Brazil and the Andes of Qiile, and in the Old World southward to South 
Africa, Madagascar, Malay Peninsula, Java and Sumatra. 

The poplars are entirely wind pollinated. Their flowers, borne in pen- 
dent catkins, are uncolored, without scent or nectar and unattractive to 

The willows and poplars are undoubtedly closely related though they may differ 
markedly in appearance. The leaves of the willows are mainly short stalked and linear, 
generally dark green above and whitened beneath, while those of the poplar are generally 
orbicular and long stalked, often with the stalk flattened laterally, at right angles to 
the blade, so that in a light breeze it is caused to twist into a vertical position as it 
gives before the air pressure, imparting to the leaves their characteristic trembling 
motion, whereas the leaves of the willow are lifted without twisting out of the horizon- 
tal. This is most beautifully expressed by TENNYSON in the lines : 

Willows whiten, aspens quiver, 
Little breezes dusk and shiver 
Thro' the wave that runs forever 
By the island in the river 
Flowing down to Camelot. 

Roger P. Wodehouse 62 Hayfever Plants 

Salix (The Willows) 

The willows are trees or shrubs with scaly bark, slender tough branch- 
lets often easily separating at the joints, simple, alternate leaves, generally 
lanceolate or linear, occasionally obovate or rotund, pinnately veined (fig. 

The pollen grains (fig. 31B) of all species are essentially alike, sphe- 
roidal or oblately flattened, three lobed, ellipsoidal when dry, about 17.8^ 
in diameter, generally with three meridionally arranged furrows, exine 
reticulate with vertical edges which are thin and blade-like on their crests 
but thickened toward their bases. The reticulum is of coarser mesh toward 
the centers of the lunes, finer toward the poles and sharply bounded along 
the margins of the furrows with much smaller lacunae. The furrows are 
long and tapering, their membranes flecked as if covered with detached 
fragments of the exine, without a true germ pore but generally with a 
central bulge representing the germinal papilla. Willow pollen grains 
resemble somewhat those of the Caprijoliaceae, Oleaceac and Sterculeaceae, 
but they may be distinguished from the first by their lack of a sharply 
defined germ pore, and from the two latter by their smaller size. 

There are about 150 species of willow in North America. 'The genus 
has long and justly been considered a difficult one to study. It is not that 
the genus is so large .... or that the species are so variable in themselves, 
although a few of them are known to be very much so. The chief difficulty 
lies in the dioecious character of the plants, and the fact that in the majority 
of the species the flowers are produced before the leaves appear, or at least 
before they are large enough to become characteristic" (BALL 1900). 
Roughly speaking the willows are of two general types, those in which the 
catkins appear in advance of the leaves (the pussy willows) and those in 
which the catkins appear at the same time as the leaves. The pussy willows 
are mostly shrubs, and flower very early in spring, sometimes while snow 
is still on the ground, in the northeastern states as early as March. Those 
of the second group may be trees or shrubs or even, in the alpine and arctic 
species, almost herbaceous. 

Among the pussy willows the European purple osier (S. purpurea L., 
fig. 28) is one of the most frequently cultivated for the beauty and luxuri- 
ance of its staminate catkins, the first heralds of spring so popular with 
children, and its long purple shoots which may be woven into baskets. It 
has become sparingly established in the Atlantic coast states, Ontario and 
Ohio. A wild native species commonly called pussy willow or silver willow 
(S. discolor Muhl.) is widely distributed in swamps and moist places 
throughout most of the northern United States and Canada, except far 
west. Among the tree forms the black or swamp willow (S. nigra Marsh.) 
is perhaps the largest and best known. It reaches a height of 120 feet with 
a trunk diameter of three feet, occurring along streams and on the shores 
of lakes and ponds throughout the United States and Canada, principally 
east of the Rocky Mountains. It is reported by WATRY and LAMSON 
(1931) as occurring in Needles, California, but unimportant in hayfever. 
The crack, brittle or snap willow (S. fragilis L.) having been introduced 

Chapter III 



into cultivation in America from Europe, has escaped and become thor- 
oughly established in the Atlantic states and as far west as Kentucky. It is 
one of the commonest in villages and small towns. Both its English and 
Latin names refer to the fact that the twigs are easily detached from the 
main stem. As they fall they come down with the butt end first and often 
stick into the soft mud in an upright position and take root or, if they fall 
into the water, they may float away to establish new colonies wherever 
they become stranded. This characteristic is very convenient for the pollen 
collector ; it is only necessary for him to shake a flowering tree vigorously, 
then pick up the fallen twigs with their yellow catkins. The white willow 
(S. alba L.) and the weeping willow (S. babylonica L.), two very beautiful 

FIG. 28. Willow flowers (SalLv pur pur ea). 

introduced species, the one from Europe the other from Asia, are much 
planted in parks and along streams. 

Though each species of willow has a relatively short flowering period 
there are so many of them that the willow pollen season may extend for 
more than two months, starting in March and lasting until June, or even 
longer where some of the late-flowering species occur. Apparently no 
attempt has ever been made to distinguish between the different willows in 
hayfever studies; indeed any such distinction seems to be unnecessary. 
Though willow pollen is frequently caught in abundance on atmospheric 
pollen slides all available evidence seems to show that it is of only minor 
and incidental importance in hayfever. 

Roger P. Wodehouse 64 Hayfever Plants 

For a further study of this interesting group the reader is referred to 
the works of BALL (1924 and pp. 128-139 in COULTER and NELSON, 1909) 
and SARGENT (1922). 

Populus (The Poplars, Aspens and Cottonwoods) 

The poplars are small or large trees, with pale smooth furrowed hark, 
light brittle wood, scaly resinous buds and long petioled leaves (fig. 29). 
They are dioecious with their flowers in long pendent drab colored catkins, 
opening before or at the same time as the leaves, generally very early in 

Their pollen grains (fig. 3 1C) are spheroidal or more or less deformed 
as if by pressure from each other within the anther, without pores or fur- 
rows, 27 to 34/x in diameter. The exine is thin and fragmentary consisting 
of a network of granules spread loosely and thinly over the intine. The 
latter is thick and hyaline. These grains bear no obvious resemblance to 
those of the willows, since the characteristic exine of the latter is here a 
vanishing remnant. Still in the faint suggestion of its reticulate structure 
it seems to show family relationship with the willows. Wind pollination 
almost invariably leads to a reduction in the thickness of the exine with an 
attendant loss of its sculpturing, and a compensating increase in the thick- 
ness of the intine. The pollen grains of the poplars, as compared with those 
of the willows, are an outstanding example of this law. 

In keeping with their mode of pollination exclusively by wind the 
flowers of the poplars are uncolored, unscented and not provided with 
nectar. They generally have more stamens than those of the willows and 
produce very much more pollen which is not at all sticky and is known to 
be carried great distances by the wind. 

The genus comprises about 34 species of which about 15 are found in 
North America. They range from the Arctic circle to northern Mexico 
and Lower California and from the Atlantic to the Pacific, in the New 
World, and from the Arctic to northern Africa, the southern slopes of the 
Himalayas, central China and Japan, in the Old World. In the extreme 
north the poplars form great forests, and are common on alluvial bottom 
lands of streams and on high mountain slopes. 

In cities several species, in America mostly introduced, are favorite 
trees for street planting. The white or silver poplar (P. alba L.) also called 
abele, is a European species commonly planted on streets and in yards. 
It is a large tree with broad leaves, dark green above and white and downy 
below. Its leaf petioles are not flattened, consequently its leaves do not 
have the trembling motion characteristic of most species. Another intro- 
duced species is the black poplar (P. nigra L.) native of Europe and Asia. 
Its characteristic form is round headed pyramidal, and of medium height, 
but it is exceedingly variable. Many of its varieties have been named ; one 
of these is the tall graceful columnar form known as Lombardy poplar (var. 
italica DuRoi) extensively planted along city streets and as a wind break. 
Its leaves are small and triangular, smooth and green on both sides, the 
leaf stalks flattened. Also involved in street planting are a number of 

FIG. 29. POPLAR AND WILLOW LEAVES: A, Valley cottonwood (Populus Wislizc- 
nii) ; B, California cottonwood (P. Fremontii) ; C, Quaking aspen (P. tremuloidcs) ; 
D, Crack willow (Salix frayilis) ; E, Western cottonwood (P. Sargentii} ; F, Large- 
toothed aspen (P. grandidentata} ; G, Willow-leaved or Mountain cottonwood (P. an- 
gustijolia) ; H, Cottonwood (P. tcxmia} ; I, Cottonwood (P. Fremontii}. 

Roger P. Wodehouse 66 Hayfever Plants 

hybrids between P. nigra and P. balsamifera (REHDER 1940). These are gen- 
erally known as Carolina poplars or P. canadensis Moench among horticul- 
turists, though the group can not be regarded as a botanical species ; it is 
rather a collection of hybrids. Most of them occur only in the staminate form 
and are always propagated vegetatively so that every tree of each variety is 
really a part of the original hybrid, horticulturally spoken of as a clone. One 
of the best known of these is the Eugene poplar, known to horticulturists as 
P. canadensis Eugeni Schelle or as P. Eugenei Simon-Louis, which origi- 
nated near Metz, Lorraine. 

There are also many native species which must be considered in hay- 
fever studies. Even when these do not grow near dwellings they may be 
effective in causing hayfever on account of the buoyant nature of their 
pollen. One of the commonest and most widely distributed is the quaking 
or trembling aspen (P. tremuloides Michx.) also called American aspen or 
quiver-leaf. It is a small graceful tree scarcely exceeding 40 feet in height, 
with small leaves green on both sides and with finely serrate margins, their 
petioles very much flattened. It is found on the borders of streams, lakes 
and in meadows almost throughout Canada from Newfoundland to Alaska 
and southward to New Jersey, Kentucky, Nebraska and California, and in 
the Rocky Mountains following the Canadian zone even into Mexico. Its 
flowering period, generally of only a few days duration in any locality, 
occurs between March and May, depending upon the climatic factors of 
the locality. Another poplar of wide distribution is the tacamahac, balsam 
or Carolina poplar (P. tacamahaca Mill.). It is a tall tree with leaves green 
on both sides and with round petioles. It ranges from Newfoundland to 
Alaska wherever trees can grow, and southward as far as Oregon and 
New York. It flowers in April. This species is sometimes known as 
P. balsamifera DuRoi and as a consequence confused with P. balsamifera L. 
which is quite different. It occurs in several varieties. The balm of 
gilead (P. tacamahaca candicans Gray, P. candicans Ait.), known only in 
the pistillate form, is often considered one of them (SARGENT 1922). 

In the northeastern states are two other common species, one the large- 
toothed aspen (P. grandidentata Michx.) easily recognized by its coarsely 
toothed leaves, which are green on both sides and with flattened petioles. 
It has a range from Nova Scotia to Minnesota and southward to Tennessee. 
The other, often associated with it, is the cotton wood (P. balsamifera L., 
P. angulata Michx. f.) a large tree with massive spreading branches, with 
deeply furrowed gray or brown bark. The species ranges from Vermont to 
Mississippi but is not common. However several varieties occur; one of 
these P. balsamifera virginiana Sarg. (P. virginiana Fougeroux, P. del- 
toidea Marsh) is the common cotton wood of the East, generally going by 
the name of P. deltoides, necklace poplar. Two other varieties, var. pilosa 
Sarg. and var. missouriensis Rehd. occur in the South. 

In the Rocky Mountains are found still others. The western or river 
cottonwood (P. Sargentii Dode) is similar to the necklace poplar; it is even 
regarded by some as a variety of it (P. deltoides occidentalis Rydb.). It is 
the principal tree in the eastern foothills of the Rocky Mountains, ranging 

Chapter III 67 Angiosperms 

through the mountainous sections from Saskatchewan to New Mexico and 
eastward to the Dakotas, Nebraska and Kansas. It flowers in March and 
April and is probably the cause of some hayfever. On the western slope 
of the Rocky Mountains is found the willow-leaf cottonwood (P. angusti- 
jolia James) also known as black, mountain or narrow-leaved cottonwood. 
It is the common cottonwood of the Rocky Mountain region reaching from 
western North Dakota, southern Saskatchewan and eastern Washington 
southward to northern New Mexico and Arizona. It flowers in April and 
May and seems to be the cause of some hayfever. Rydberg's or smooth- 
barked cottonwood (P. acuminata Rydb.) is a similar tree but with leaves 
rhombic lanceolate to ovate. It is found on the banks of streams throughout 
the Rocky Mountain region from Saskatchewan to western Texas and to 
eastern Utah and Montana. It is sometimes planted as a street tree. The 
valley cottonwood (P. Wislizenii Sarg.) is a large tree with spreading 
branches and deltoid coarsely toothed leaves. It occurs in western Texas, 
New Mexico and part of Colorado, and is perhaps the most familiar tree 
in New Mexico. It is especially common in the flood plains of the Rio 
Grande and San Juan River, and is the most commonly planted shade tree 
of the cities. It flowers in March and April and is believed to be an impor- 
tant cause of hayfever. 

In the far west are two other species, the California cottonwood and 
the Arizona cottonwood, which are believed to cause some hayfever. Cali- 
fornia cottonwood (P. Fremontii Wats.) also known as Fremont's cotton- 
wood, is a tall tree reaching 100 feet in height and with trunk diameter of 
five to six feet, with broad coarsely toothed leaves, green on both sides and 
with flattened petioles. It is found on the Pacific coast of California and 
part of Lower California and especially in the San Joaquin valley, and is 
often planted as a shade tree in southern California. It flowers in February 
and March and is believed to be an important cause of hayfever. Arizona 
cottonwood (P. McDougallii Rose), the cottonwood of the Colorado River 
delta, is similar and closely related; in fact it is sometimes regarded as 
merely a variety. It is found near springs and on the banks of streams 
from San Bernardino County, Nevada, to Yuma, Arizona, where it is 
probably the only cottonwood occurring naturally. It is also planted as a 
street tree in the towns of southern California. 

Betulaceae (The Family of the Birches, Alders, Ironwood and Bluebeech) 

The Betulaceae are trees or shrubs with slender branchlets marked by 
numerous pale lenticels; their leaves pinnately veined, doubly serrate, 
deciduous; their flowers monoecious in pendent catkins, opening in spring 
either before or at the same time as the leaves. Their pollen grains are 
smooth or faintly granular, spheroidal or oblately flattened, 20 to 40/x in 
diameter, provided with 3 to 7 germ pores which tend to be equally spaced 
around the equator, generally somewhat protruding and giving the grain an 
angular outline. 

The family comprises six genera confined to the northern hemisphere; five are 
native of North America. All species are wind pollinated and shed exceedingly large 

Roger P. Wodehouse 


Hayfever Plants 

amounts of pollen. The birches themselves are known to occasionally cause severe 
hayfever, but it is not known what part the other members of the family play. In view 
of the close relationship existing between the several genera, however, it is to be ex- 
pected that sensitization to the pollen of the birches would generally imply sensitization 
to that of the other members of the family. 

Betula (The Birches) 

The birches are trees with smooth tough resinous bark marked by 
numerous horizontal lenticels serving as breathing pores. In the younger 
trees the bark generally has a tendency to separate in papery layers but may 
become deeply furrowed and scaly at the base of old trunks. The pistillate 
catkins persist throughout most of the winter as conspicuous brownish 
cones with slowly deciduous scales, discharging their small winged seeds 
which are blown about the surface of the snow. The staminate flowers are 
borne in long pendulous catkins (fig. 30) which fall off as soon as they shed 
their pollen. 

FIG. 30. White birch flowers (Betula alba). 

The pollen grains (fig. 31 D) are flattened angular, 20 to 40/u, in diameter 
(less than 30/x in American species) ; with three pores, or occasionally some 
grains with four and higher numbers up to 7, equatorially arranged, 
strongly aspidate and protruding, imparting to the grain its angular appear- 
ance, their apertures broadly elliptical and meridionally oriented or, if there 
are more then three pores, biconvergent. The exine is nearly smooth or 
slightly granular. Birch pollen grains are scarcely distinguishable from 
those of Carpinus. In fact it is only with difficulty that they can be distin- 
guished from those of most members of the Betnlaceae and Myricaceae. 
For a detailed discussion of this problem the reader is referred to "Pollen 
Grains" ( WODEHOUSE 1935). 

Chapter III 



The birches flower early in spring, generally just before or at the time 
of the unfolding of the leaves, in the northeastern United States and Canada 

(Juncus) ; B, Willow (Salix) ; C, Poplar (Populns) ; D, Birch (Betula) ; E, Alder 
(Alnus) ; F, Bluebeech (Carpimts) ; G, Ironwood (Ostrya) ; H, Hazel (Corylns) ; 
I, Beech (Fagus). All magnified 1300 times. 

late April or early May, thus following by several weeks the poplars, hazels, 
pussy willows and elms. They shed large quantities of pollen which is 
known to be among the most important tree pollens in hayfever. The 

Roger P. Wodehouse 70 Hayfever Plants 

flowering period of each species is short, generally less than a week, but 
those of the different species do not coincide so the birch hayfever season 
may last several weeks, or about a month where several species are involved ; 
they appear to be about equally effective in causing hayfever and aller- 
genically indistinguishable. 

In the northern United States three species, the gray or white birch, 
the yellow or gray birch and the cherry or black birch, are often found grow- 
ing together. They flower in succession, beginning in April or May with 
the gray birch and ending several weeks later with the black birch. The gray 
or white birch (B. popitlifolia Marsh.), sometimes called the American 
white birch, is only a small weak tree and short lived, but graceful and 
beautiful, characteristic of dry gravelly barren soil and depleted farm lands 
from Nova Scotia to Delaware and westward to Wisconsin, Minnesota and 
western Ontario. Its bark tends to separate in papery layers, but sheets 
large enough to be of any practical use can not be obtained. The black or 
cherry birch (B. lenta L.) is a large forest tree reaching 80 feet with dark 
brown almost black bark with no tendency to separate in layers but 
which gives the trunk a decided resemblance to that of a cherry tree. Its 
twigs and leaves have a pleasant wintergreen odor ; in fact an oil which is 
distilled from the twigs is the 'oil of wintergreen' of commerce. This species 
has a more southerly distribution from New England to Florida and west- 
ward to Minnesota. The yellow or gray birch (B. lutea Michx.) is also a 
large forest tree, reaching a height of 100 feet with a trunk diameter of four. 
Its bark is yellowish or grayish and separates in lustrous layers no thicker 
than tissue paper which may often be seen decorating the trunks of old 
trees with rows of silvery curls, particularly the trees which are found deep 
in the forest where they are protected from winds. This species has a more 
northerly distribution, from Pennsylvania and Connecticut to Newfound- 
land, and westward to Manitoba. 

In the South occurs the red birch (B. nigra L.), also known as river or 
water birch. It is a tall tree reaching 100 feet in height. On young trees 
and large branches the bark is of a silvery or brownish lustre and separates 
freely into thin papery scales, but on old trees the bark is dark reddish 
brown and deeply furrowed. It is the common birch of the southern states 
where it is found on the banks of streams, ponds and swamps, in deep 
rich soil, from Connecticut to Florida and westward to Minnesota and 

The common birch of Canada is the paper or canoe birch (B. papyrifera 
Marsh.) a tall and valuable forest tree, extending almost throughout Canada 
and southward to Pennsylvania, Michigan, Nebraska, Wyoming and Mon- 
tana and, in its several varieties, reaching to Washington. Its white bark 
which may be stripped in a single piece from the whole trunk has furnished 
the northern tribes of aboriginal Americans their canoes and many utensils, 
and its wood, though light and soft, has many uses. 

The cultivated birches are principally varieties of the Asiatic and Euro- 
pean B. pendula Roth or B. alba L. The latter flowers a week or more 
earlier than the native birches in the northeastern United States. 

Chapter III 71 Angiosperms 

Alnus (The Alders) 

The alders are shrubs or trees with broad, toothed leaves, pinnately 
veined, and alternately arranged on their branches. The flowers of both 
sexes are borne in catkins (fig. 32), the staminate pendulous and early 
deciduous, the pistillate more or less erect with woody scales and persistent, 
expanding very early in spring before the leaves, or toward the end of 

Their pollen grains (fig. 3 IE) are oblately flattened, angular, 19 to 
27/x in diameter, with 4 or 5, rarely 3 or 6 germ pores which are aspidate, 
with markedly thickened rim and protruding, their apertures narrowly 
elliptical or slit shaped. The texture of the exine is smooth or slightly 
granular. A striking character of these grains is their possession of band- 
like thickenings of the exine extending in broad sweeping curves from pore 

FIG. 32. Alder flowers (Alnus'). 

to pore in pairs, one on either side of the equator. These serve to distin- 
guish alder pollen grains from all others of the same general character. 

Nine species are native of North America, and the European black alder 
(A. vulgaris Hill) is sometimes cultivated, and has become naturalized 
locally in the northeastern states. Of the native species the speckled or 
hoary alder (A. incana Moench) is a shrub 8 to 40 feet high, widely dis- 
tributed from Newfoundland to Saskatchewan and southward to Nebraska, 
Ohio and Pennsylvania. Smooth or tag alder (A. rugosa Spreng.) is a 
shrub of similar appearance but has a more southerly distribution, from 
Maine to Florida and westward to Texas, Nebraska and Minnesota. It 
flowers very early, in March or April, even in January and February in 
the southern part of its range, among the very first flowers of spring. In the 
western part of the country are two alders large enough to properly be 
regarded as trees. The Sitka or wavy-leaved alder (A. sinuata Rydb.) is a 
small tree attaining a height of 45 feet common along mountain streams and 
lakes where it often forms dense thickets in the Canadian and Hudson Zones 

Roger P. Wodehouse 


Hayfever Plants 

from Alaska to Oregon and eastward to Saskatchewan and Colorado. It 
flowers late, the flowers appearing with or after the leaves from May to 
July. The white alder (A. rhombijolia Nutt.) is a small tree, sometimes 
reaching a height of 75 feet, the common alder of the valleys of central Cali- 
fornia. It ranges from northern Lower California to southern British 
Columbia and eastward to the western slope of the Rocky Mountains in 
Idaho. It flowers in winter or early spring, generally December or January. 

Garpinus (Hornbeam or Ironwood) 

The hornbeams are trees or shrubs with smooth gray bark, and fur- 
rowed or ridged stems. The flowers (fig. 33) open before the leaves, in 

FIG. 33.- 

-American hornbeam staminate and pistillate catkins (Carpinus caro- 

April or May, the staminate in short pendent catkins, the pistillate in short 
terminal spikelets. Each flower is subtended by a flattened bract which 
enlarges at maturity to resemble a three pointed leaf. The pollen grains 
(fig. 31 F) are similar to those of birch but more nearly circular in outline 
when seen in polar view, about 26.5/x in diameter, though there is some vari- 
ation in their size. They have three or four pores, in the American horn- 
beam generally three, in the European generally four. The pores are small, 
nearly circular and capped by a small operculum. Their rims are scarcely 
thickened yet the pores bulge prominently. The exine is smooth except 
around the pores where it may be slightly granular. 

The genus comprises about 15 species distributed almost throughout 
the northern hemisphere. The American hornbeam or bluebeech (C. caro- 

Chapter III 73 Angiosperms 

liniana L.), the only species native of North America, is a small tree common 
in the eastern United States in moist woods and along streams from Nova 
Scotia to Minnesota and southward to Florida and Texas. It flowers just 
before the birches and its pollen is frequently caught on pollen slides. The 
European hornbeam (C. Betula L.) is a fair sized tree, reaching 70 feet and 
is commonly planted in North America. The pollen of both species reacts 
cutaneously with hayfever patients and appears to be a complicating factor 
in cases of birch hayfever. 

Ostrya (Hop-hornbeam, Ironwood) 
The iron woods (fig. 34) are small trees with scaly bark, with terminal 

FIG. 34. Hop-hornbeam (Ostrya virginiana). 

pistillate catkins, their flowers in pairs subtended by a persistent bractlet 
which enlarges into a bladder-like sac, making the catkins look like hops at 

The pollen grains (fig. 31G) are similar to those of birch, about 27. S^ 
in diameter, slightly flattened oblately and somewhat angular in outline, with 
generally three pores, rarely four, their apertures nearly circular and their 
membranes flecked with granules which tend to be aggregated toward the 
center, not forming a sharply defined operculum as in the grains of Car- 
pinns. The exine is decidedly granular throughout, and the subexineous 
thickenings underlying the pores are very much smaller than in the grains 
of Carpinits. 

The genus comprises four species, two of them native of North America. 
The hop-hornbeam (0. virginiana Willd.), also called ironwood, hardback 
or leverwood, is generally a small tree but may reach a height of 50 or 60 
feet. It is common and widely distributed from Cape Breton Island to 
Manitoba and southward to Florida and Texas. It flowers in April or May 
shedding large amounts of pollen. 

Roger P. Wodehouse 


Hayfever Plants 

Gorylus (Hazels or Filberts) 

The hazels are shrubs or small trees. Their staminate flowers are borne 
in long pendent catkins (fig. 35), their pistillate flowers few in clusters at 
the ends of branches, maturing to form large nuts wrapped in their in- 
volucres of leaf-like bracts which may be distinct, or united into a tubular 

The pollen grains (fig. 31 H) are similar to those of the birches but their 
pores, which are always three, less raised and their apertures nearly or 
quite circular. 

The genus comprises 7 species of Europe and North America. The 
European species, (C. Avellana L.), the common hazelnut or filbert, is the 
one most frequently planted in America. It occurs in many varieties which 
are cultivated for their fruits or for ornaments. Three species are native of 

FIG. 35. Hazel flowers (Corylus). 

North America. In the eastern states the American hazel (C. americana 
Walt.) and the beaked hazel (C. rostrata Ait.) often grow together in 
thickets and along roadsides. Both are small shrubs, so similar to each 
other that it is difficult to tell them apart when they are not in leaf. The 
leaves of the beaked hazel, however, may be distinguished by their incised 
and serrate margins from those of the American hazel which are merely 
serrate. In their fruits the distinction is more marked ; that of the American 
hazel is enclosed in two broad laciniate bracts giving it something the 
appearance of an old fashioned bonnet, from which it is called the bonneted 
hazelnut or filbert. The involucral bracts of the beaked hazelnut are united 
and prolonged into a tubular bristly beak to which both its English and Latin 

Chapter III 75 Angiosperms 

names refer. Both species flower very early in spring. All winter long 
the staminate catkins of the hazels may be seen hanging stiffly from the 
young branches, but at the first suggestion of spring they lose their stiff- 
ness, open their flowers and shed their pollen, which is copious enough to be 
caught on pollen slides, and is among the first to make its appearance, 
usually together with the first few grains of pine and jumper pollen. In the 
East these two species have much the same distribution ; the American hazel 
extends from Maine to Florida and westward to Montana and Wyoming, 
while the beaked hazel extends from Nova Scotia to Georgia and westward 
to Oregon and British Columbia. On the Pacific coast in the moist canyons 
of the Transition Zone from British Columbia to California is found the 
California hazel (C. calif ornica Rose) similar to the beaked hazel both in 
the double toothed character of its leaves and its beaked fruits. In fact it is 
frequently regarded as a variety and designated as C. ro strata calif ornica 
A. DC. 

Fagaceae (The Beeches, Oaks, Chestnuts and Chinquapins) 

The beech family includes six genera and about 400 species of trees and 
shrubs of wide distribution but mainly confined to the northern hemisphere. 
The five genera, Fag us, the beeches ; Quercus, the oaks ; Castanea, the 
chestnuts ; Castanopsis, the chinquapins ; and Lithocarpus, the tan-bark oaks, 
are represented in America ; the sixth genus, Nothojagus, is established to 
receive the beeches of the southern hemisphere. All are monoecious, the 
staminate flowers borne in unisexual heads or in erect or pendent catkins, 
usually appearing in late spring or early summer, at about the same time 
that the leaves unfold, or shortly after. The beeches and oaks are entirely 
wind pollinated and are characterized, especially the latter, by the enormous 
quantities of pollen they shed. The chestnuts, chinquapins and tan-bark oaks 
are primarily insect pollinated. Their staminate catkins are stiff and more or 
less erect, never pendent as in the oaks and most other wind pollinated 
forms, they produce much less pollen than the oaks and beeches, and are 
characterized by a strong disagreeable odor, and succeed in attracting to 
themselves many honey-gathering insects. 

The pollen grains of the oaks (fig. 40A) and beeches (fig. 311) are 
similar to each other, being of medium size and provided with a rather thin 
and warty-granular exine. But they bear no resemblance to those of the 
chestnuts and chinquapins which are very small and provided with a per- 
fectly smooth exine. The difference between these two types of grain is far 
greater than should be expected between plants closely enough related to 
belong to the same family, and appear to be the result of adaptations to their 
respective modes of pollination. 

Fagus (The Beeches) 

The beeches are trees with smooth light-gray bark, and yellowish-green 
staminate flowers in heads, opening at the same time as the leaves. The 
pollen is buoyant and easily dispersed by the wind, and is frequently caught 

Roger P. Wodehouse 


Hayfever Plants 

on pollen slides, but is generally much less abundant than that of oaks. The 
grains (fig. 311) are approximately spherical, about 40/x in diameter with 
three long tapering furrows meridionally arranged, their margins slightly 
raised, their membranes smooth and provided with a small elliptical germ 
pore. Underlying each pore within the cell is a small globular hyaline body. 

The genus comprises four species of the northern hemisphere. Only one, the Amer- 
ican beech (F. grandifolia Ehrh.), however, is native of North America, ranging from 
Nova Scotia to Florida and westward to Missouri and Texas. Two others occur in 
eastern Asia and one in Europe. This latter (F. syhatica L.) is the species generally 
cultivated in the United States. It occurs in several varieties of widely different ap- 
pearance, the commonest of which are those having pendulous branches, pyramidal 
habit, leaves purple or deeply cut. The European species appears to shed very much 
more pollen than the native American species, but neither appears to be more than a 
minor contributory factor in hayfever. 

FIG. 36. White oak (Qucrcus alba], flowering twig. 

Quercus (The Oaks) 

The oaks are noble deciduous or evergreen trees, rarely shrubs. Their 
staminate flowers are borne in slender pendulous catkins (fig. 36), with 
usually six-parted calyx and 4 to 12 stamens, opening at the same time as or 
just after the unfolding of the leaves, generally in May. The oaks shed 
enormous quantities of pollen, outranking that of all other plants in regions 
where the trees are abundant. Oak pollen has to its credit rather more 
hayfever cases than most trees but the number is in no way commensurate 
with the amount of pollen they shed. 

Chapter III 77 Angiosperms 

Oak pollen grains (fig. 40A) are spheroidal or oblately flattened and 
triangular in outline, tricolpate or, occasionally, some grains with super- 
numerary furrows, the latter arranged according to the trischistoclasic sys- 
tem, long and tapering to pointed ends, their margins not raised, their mem- 
branes smooth and provided with a small pore, but the furrow membranes 
are invariably ruptured when the grains are prepared for microscopic 
examination unless special precautions are taken to prevent its occurrence. 
Underlying the center of each furrow, within the body of the cell, is a wedge- 
shaped hyaline body centripetally oriented. The exine is rather thin but 
coarsely warty -granular and the intine thick. 

The genus comprises about 275 species of the northern hemisphere, ex- 
tending into the tropics in mountainous districts. About 65 are native of 
North America, and a few European species as the English oak (Q. Robitr 
L.), the cork oak (Q. suber L.), and Q. sessiliflora Salisb. are cultivated to 
a limited extent in the eastern states. 

Taxonomically the oaks are exceedingly difficult. This is partly because 
many species are variable and exhibit a strong tendency to form natural 
hybrids, and often the differences between species are very slight. However 
this fact probably makes it unnecessary for hayfever students to distinguish 
them precisely. For example, BROWN (1932) states "There are at least 
twenty different species growing in the Middle Atlantic States but they are 
all so closely related that an oak pollen mixture is sufficient for routine 
testing". The English names are often used to designate groups of species 
which are related or similar rather than individual species, a procedure 
which though not strictly scientific is eminently practical. According to 
their natural relationships the genus may be roughly divided into four 
groups, the Black Oaks, Willow Oaks, White Oaks and Chestnut Oaks. 
Besides these groups which are based on actual relationship other English 
group-names bring together those which are similar though not necessarily 
closely related. Thus the Live Oaks are those which retain their leaves 
throughout the winter these include some of the willow oaks and white 
oaks. The Scrub Oaks are those which do not grow into tall trees and often 
form dense thickets. These are mostly red or white oaks. 

The Black Oaks : These are distinguished by having their leaves 
deeply lobed and the lobes pointed and tipped with a bristle (fig. 37A). 
Their fruit matures at the end of the second season and the cup of the acorn 
is silky inside. Their minute greenish flowers have 4 to 6 stamens. Perhaps 
most representative of the Black Oak group is the black oak itself (Q. velu- 
tina Lam.) and the red oak (Q. rubra L., fig. 37B). At any rate these are 
the best known and the most widely distributed members of the group in the 
eastern United States. They have nearly the same range, both extending 
from Maine to Florida, and westward to Minnesota and Kansas, with the 
red oak reaching northward into Nova Scotia and the black westward into 
Texas. Other common species of this group are the gray or red oak (Q. 
borealis Michx. f.) extending from Nova Scotia to Florida and westward to 
Kansas, the scarlet oak (Q. coccinia Wang.) also known as Spanish, black 

Roger P. Wodehouse 


Hay fever Plants 

or red oak, with a distribution from Maine to North Carolina and westward 
to Ontario and Missouri, and the Spanish, swamp or pin oak (Q. palustris 

FIG. 37. OAK LEAVES: A, Black oak (Quercus velutina) ; B, Red oak (Q. ru- 
bra) ; C, Scrub oak (Q. ilicifolia) ; D, Spanish oak (Q. palustris) ; E, Willow oak 
(Q. Phellos) ; F, Coast live oak (Q. agrijolia) ; G, Scrub oak (Q. venustula) ; H, 
White oak (Q. alba) ; I, Live oak (Q. virginiana) ; J, Swamp white oak (Q. bicolor) ; 
K, Chestnut oak (Q. Prinus). 

DuRoi, fig. 37D) which is generally a smaller tree with slender drooping 
branches. It has a more restricted range, reaching only from Massachusetts 
to Virginia and westward to Michigan and Arkansas. 

Chapter III 79 Angiosperms 

Also belonging to this group are the two species known as black-jack 
oak (Q. marilandica Muench. and Q. nigra L.). The former is also called 
barren oak and is characteristic of dry sandy or clay barrens, from Long 
Island and Staten Island southward to Florida and westward to Nebraska 
and Texas. The latter is also called water, pin, spotted, duck, or 'possum' 
oak and is characteristic of high sandy borders of swamps and streams and 
rich bottom lands throughout the southeastern states from Delaware to 
Florida and westward to Missouri and eastern Texas. It is commonly 
planted as a shade tree in the streets and squares of southern cities. 

The Willow Oaks are similar to the black oaks, except that the leaves 
are not generally lobed (fig. 37E) ; instead they are lanceolate, ovate or ob- 
long and with their margins entire or merely toothed. The group is small 
and could quite properly be regarded as a subdivision of the Black Oaks. The 
most representative species is, perhaps, the willow oak (Q. Phellos L., fig. 
37E), a large tree characteristic of the coastal plane and adjoining territory, 
in swamps and on banks of streams and sandy bottoms from southern New 
York to Florida and westward to Texas and Missouri. Also belonging to 
this group are the western live oaks which will be discussed later. 

The White Oaks comprise some of our largest and handsomest mem- 
bers of the genus. They may generally be easily distinguished from those 
of the previous groups because their leaves are lobed (fig. 37H) and the 
lobes rounded and not bristle tipped. The fruit matures at the end of the 
first season, and the cup of the acorn is quite smooth inside. The bark is 
generally flaky and light in color. The most representative species is the 
white oak (Q. alba L.), a large forest tree reaching 100 feet in height and 
with a broad spreading crown of thick heavy branches. It is one of the most 
abundant species throughout the eastern states from Ontario to Florida and 
westward to Minnesota and eastern Texas. Others of this group are the 
post or iron oak (Q. stellata Wang.) characteristic of dry sterile and acid 
soils such as Cape Cod and the islands of southern Massachusetts south- 
ward to Florida and westward to Iowa, western white oak (Q. Garryana 
Dougl.) also called Garry's or Oregon oak, of the Pacific coast where it is 
rather rare and local, confined to valleys and dry gravelly slopes from Van- 
couver Island southward to Oregon and northern California, but it has the 
distinction of being the only oak in British Columbia. Also of the Pacific 
coast is the evergreen, mesa or Engelmann's oak (Q. Engebnannii Greene). 
The leaves of this are persistent throughout the winter but fall with the 
appearance of the new leaves in spring. It is confined to the mountains of 
southern California. 

The Chestnut Oaks, except that the leaves are sinuately toothed rather 
than lobed, are similar to the White Oaks. The most representative species 
is that of the chestnut oak (Q. Prinus Engelm.) with leaves elongate 
coarsely toothed and closely resembling those of the chestnut (fig. 37K). It 
is a large tree, with thick and deeply furrowed bark, characteristic of rocky 
banks and hillsides from Maine to Alabama and westward to Tennessee. 

Roger P. Wodehouse 80 Hayfever Plants 

Also belonging to this group is the swamp white oak (Q. bicolor Willd.) 
which closely resembles the white oak, having leaves more nearly pinnatifid 
(fig. 37J) than toothed and with similar whitish flaking bark. It is a large 
and stately tree of less spreading habit than the white oak, on borders of 
streams and swamps from Quebec to Georgia and westward to Minnesota 
and Arkansas. 

Live Oaks : Regardless of their botanical group, many of the ever- 
green oaks are called Live Oaks. Usually their leaves are thick and leathery 
and very stiff and more or less evergreen. Three of these are western. The 
coast live oak or encina (Q. agrifolia Nee) is a large and beautiful spread- 
ing tree with leathery prickle-tipped leaves (fig. 37F) falling during winter 
and early spring, native of the coastal regions of California. The interior 
or highland live oak (Q. Wislizenii A. DC.) is somewhat similar but with 
leaves deciduous during their second summer and autumn, native of the 
interior of California. The maul oak (Q. chrysolepis Liebm.) is similar but 
of wider distribution in Oregon and California and with leaves falling mostly 
not before their third or fourth year. All three of these are regarded botan- 
ically as Willow Oaks. In common parlance, however, they are the live 
oaks so characteristic of the landscapes of California. Three other species 
of live oak belong to the southeastern area of the United States. Only one, 
the eastern or Texas live oak (Q. inrginiana Mill.), is a large tree, botan- 
ically a white oak. It is found principally near the coast from Virginia to 
Florida and westward to Texas and Mexico. Its leaves (fig. 37 J) fall in 
the spring with the appearance of the new set. The other two eastern live 
oaks, the dwarf live oak or scrub live oak (Q. minima Small) and the twin 
live oak or scrub oak (Q. geminata Small), are characteristic of the coastal 
plain region of the southeastern states. Botanically they are white oaks and 
so closely related to Q. virginiana that they are sometimes regarded as 
varieties of it. 

Scrub Oaks : The oaks which do not grow into large trees but, in- 
stead, tend to form thickets, are called scrub oaks or shrub oaks. Generally 
speaking, in the east the scrub oak is Q. ilicifolia Wang., also called bear or 
black oak. It is occasionally a small tree but more often a shrub forming 
dense thickets in barren, sandy or rocky soil, from Maine to North Carolina 
and westward to Kentucky and Ohio. Its leaves (fig. 37C) have short 
triangular bristle-tipped lobes and it possesses other characteristics which 
assign it to the group of black oaks. In the Rocky Mountain states are 
found two other scrub oaks, Q. venustula Greene (fig. 37G) of limited 
distribution in the Sonoran Zone of southern Colorado and northern New 
Mexico, and Q. Gunnisonii Rydb. of Submountain Zones of Colorado, New 
Mexico, Arizona and Utah. Both of these are, botanically, white oaks. The 
California scrub oak is Q. dumosa Nutt, found throughout most of Cali- 
fornia and northern Lower California. It is evergreen, its leaves falling in 
spring with the appearance of the new set, so it could quite properly be 
regarded as a live oak, but it is not spoken of as such in California for it is 

Chapter III 81 Angiosperms 

only a low shrub lacking the dignity and beauty there associated with the 
live oak. Botanically, it is, like its two eastern relatives, a white oak. 

From this brief discussion many important species have had to be 
omitted. The student who wishes to go more thoroughly into the study of 
our native oaks will find them fully discussed in SARGENT'S Manual of the 
Trees of North America. 

Gasuarinaceae (The Australian Pines or Joint-firs) 

The Casuarina family includes but a single genus of 25 species, of uncer- 
tain relationships. They are trees or shrubs with reduced leaves and jointed 
branches, giving them outwardly the appearance of primitiveness, but these 
are really characters achieved by reduction. The branchlets are green and 
function as leaves, resembling in appearance those of pine trees. Their true 
leaves are reduced to scales closely appressed in whorls around the nodes 
of the branchlets. 

The resemblance of these plants to the pines is quite remarkable, but it is 
only superficial. They are truly angiosperms and their morphological char- 
acters, especially the course of the pollen tube in entering the ovule at time 
of fertilization, indicate that they are most probably related to the walnut 

The Casuarinas are native of the Mascarene Islands, through Malaya to 
New Caledonia and Australia. Several species have been introduced into 
central and southern Florida where they are used as shade trees, windbreaks 
and sand binders. They are also often used as ornamentals and clipped as 

The Casuarinas are wind pollinated and are reported to cause some hay- 
fever (Zivixz 1942). 

C. equisctifolia Forst., Beefwood or Forestoak is perhaps the species most 
commonly planted as a windbreak and ornamental. It is noted for its rapid 
growth and is said to be capable of reaching a height of sixty feet in six 
years. It flowers sporadically almost throughout the summer and is par- 
ticularly abundant in the neighborhood of Miami. 

C. Cunninghamia is the common species of the west coast of Florida. 
It is particularly abundant in and around Tampa. It pollinates in late sum- 
mer when its flowers form conspicuous reddish brown masses at the tips of 
its branches. 

The pollen grains of the Casuarinas closely resemble those of the birch 
family and even more so those of some Asiatic species of the walnut family, 
which is strong evidence of their relationship with that group. 

Juglandaceae (The Walnut Family) 

The walnut family includes six or seven genera and about 35 species of 
tall trees with deciduous pinnate leaves, and monoecious flowers opening 
after the unfolding of the leaves. The fruit is a nut enclosed in a fleshy or 
woody shell which opens either by four valves or not of itself at all. 

Roger P. Wodehouse 


Hayfever Plants 

Only the walnuts (Juglans) and the hickories (Carya) occur in North 
America. All are wind pollinated and are noted for the large amounts of 
pollen that they shed, generally in May or early June, but their flowering 
periods are relatively short, and their pollen grains rather large, especially 
of the hickories, and not adapted to long range dispersal. Probably on 
account of this they claim only a small number of hayfever cases ; only the 
California black walnut and pecan appear to be of much importance in hay- 

Juglans (The Walnuts) 

The walnuts are tall trees with furrowed scaly bark, and large deciduous 
leaves with many leaflets, something like those of sumac. The flowers are 
monoecious appearing rather late in spring, just after the leaves unfold, the 
staminate borne in long pendent simple catkins, the pistillate solitary or 

FIG. 38. Black walnut (Juglans nigra), flowering twig. 

several together. In North America are found six native species and one, 
the English or Persian walnut (/. regia L.) introduced, probably originally 
from China, in the middle Atlantic and southern states and, in California. 

The pollen grains (fig. 40B) of the different species are all much alike. 
They are oblately flattened, 34 to 42/x in diameter, provided with 6 to 15 
pores (generally about 12) with a decidedly one-sided arrangement, occupy- 
ing all of the dorsal half of the surface and the adjoining part of the ventral, 
but leaving a large part of the latter blank. Each pore is surrounded by a 
thickened rim, those of the neighboring pores almost or quite touching each 
other so that the whole dorsal surface possesses considerable rigidity while 
the central part of the ventral surface, which has no pores, is non-rigid and 
becomes freely invaginated forming a large ventral concavity as the grain 
dries. The pores are small and elliptical, about 2.5 to 3.5/x long and so 
arranged that their long axes converge in groups of threes, or in twos at 
angles of 20 degrees. The surface of the grain is otherwise smooth except 
for its fine and faintly granular texture. 

Chapter III 



The pollen is shed in enormous quantities and in the northeastern states 
forms a conspicuous element of the atmospheric pollen collected during the 
last of May and the beginning of June. In the eastern United States are 
two species, the black walnut (Juglans nigra L., fig. 38) and the butternut 
(/. cinerea L., fig. 39). But neither of these, nor the English walnut which 
is cultivated in part of this area, appears to cause hayfever, though they have 
occasionally been suspected of doing so. 

In California are two native species, the southern California black walnut 

FIG. 39. Butternut (Juglans cinerea), flowering twig. 

(/. calij ornica Wats.) and the California black walnut (/. Hindsii Jeps.). 
Both species are much alike. Indeed, the latter is regarded by many as 
merely a variety of the former (/. calif ornica Hindsii Jeps. ) . They are fre- 
quently found around old Indian camp sites. In speaking of the California 
black walnut, the late Professor H. M. HALL (1918) says: "Much grown 
as a shade and ornamental tree in Sacramento, Napa, and Russian River 
valleys ; here the most frequent cause of spring hayfever ; less common in the 
San Joaquin valley and the south coast ranges ; occurs native especially at 
Walnut Creek and in the coastal ranges of southern California from Santa 
Ana mountains north ; common in the hills back of Los Angeles and Santa 
Monica, often near suburban homes. The southern form is var. Hindsii, 

Roger P. Wodehouse 84 Hayfever Plants 

but the pollen probably reacts interchangeably with the northern form. Pol- 
len produced in great abundance but not carried far from the trees. Posi- 
tive and virulent. April, May and perhaps early June". These two species, 
or, as Professor HALL chose to regard them, species and variety, are the 
only native walnuts of California. The English walnut, however, is exten- 
sively cultivated but seems to be here, as in the East, quite harmless to hay- 
fever patients. 

Another species similar to and often confused with the California black 
walnuts is the Arizona walnut or nogal (/. major Hell.). It is found on the 
banks of streams and in the Canyons of central and southern New Mexico 
and Arizona. Whether or not this is important in hayfever appears to be 
still unknown. It is generally listed, however, in hayfever studies from 
Arizona as a possible cause. 

Garya (The Hickories) 

The hickories are first cousins to the walnuts. Like them, they are tall 
spreading trees with smooth gray bark, on old trees becoming rough or 
scaly, with large deciduous pinnate leaves but with generally fewer leaflets 
than in the walnuts. The flowers are monoecious, appearing after the un- 
folding of the leaves. The staminate flowers are borne in long pendent 
catkins which, unlike those of the walnuts, are branched. The genus com- 
prises 17 species of which 15 are found in the United States, one in Mexico 
and one in southern China. In the United States they are principally 
eastern and do not occur in the Pacific Coast states. 

The pollen grains (fig. 40C) of the different species of hickory are all 
much alike, spheroidal or somewhat oblately flattened, about 40 to 52/* in 
diameter. Their germ pores are generally three, occasionally four or six. 
Their apertures are short elliptical or nearly circular, with their long axes 
meridionally oriented, or if more than three, converging in pairs. The pores 
are always placed slightly dorsad of the equator. Their subexineous thick- 
enings are generally very extensive, being completely fused in the grains of 
all species examined except those of pecan, but leaving a large part of the 
surface of the ventral hemisphere free of subexineous thickening, covered 
only by thin and flexible exine which may be invaginated as the grain dries 
and shrinks. 

The pollen is shed in enormous quantities and is caught on pollen slides 
in quantities equal to that of the walnuts in the late spring. 

Pecan : By far the most important hickory in hayfever is the pecan 
(C. Pecan Asch. & Graeb.). This is a good example of a tree causing hay- 
fever through cultivation. It grows naturally in the south-central part of 
the United States, from Iowa to Kentucky to Mississippi to central Texas. 
It is cultivated in a larger and only partly overlapping area, covering prac- 
tically the whole of the southern Coastal Plain, from North Carolina to 
Florida and westward to Texas and Oklahoma. It flowers from mid April 
to May. Throughout the area of its cultivation where it is used as an 
orchard and street tree, it causes a great deal of hayfever, often ranking next 
in importance to ragweed. 

Chapter HI 



The pollen of the other hickories is also known to cause hayfever where 
the trees are abundant. It is stated by BROWN (1932) to be responsible for 
quite a few cases in the Middle Atlantic States. The principal species in- 

FIG. 40. SOME TREE POLLEN GRAINS: A, Oak (Qucrcus} ; B, Black walnut (Jug- 
lans nigra) ; C, Hickory (Carya) ; D, Southern hackberry (Celtis lanngata} ; E, 
Common hackberry (C. occidentalis} ; F, Elm (Ulnius), All magnified 1300 times. 

volved are the shag- or shell-bark hickory (C. ovata K. Koch), the mocker 
nut or white heart hickory (C. glabra Sweet), and the nutmeg hickory (C. 
myristicacjonnis Nutt.). In hayfever studies the various species are not 

Roger P. Wodehouse 86 Hayfever Plants 

generally distinguished from each other because their pollens are believed 
to interreact more or less perfectly. 

Myricaceae (The Bay berry Family) 

The bayberry family comprises a small group of aromatic resinous trees 
and shrubs. The flowers are dioecious or monoecious in unisexual or 
androgynous catkins with the pistillate near the base and the staminate 
toward the tip, opening before or with the leaves. All are wind pollinated 
and shed fairly large amounts of pollen. The pollen grains (fig. 45 A) are 
almost indistinguishable from those of the Betulaceae. But this does not 
mean that the two families are necessarily related. The similarity is more 
likely due to the extreme adaptation of the members of both families to 
wind pollination. The family consists of a single genus. 

Myrica (The Wax Myrtles) 

The wax myrtles comprise about 40 species widely distributed in tem- 
perate and warm climates of both hemispheres. Seven are native to North 
America and the Asiatic M. rubra S. & Z. is occasionally cultivated. 

The species fall naturally into three groups which could quite properly 
be regarded as separate genera: (1) The sweet gale or bog myrtle (Myrica 
Gale L.) ; (2) The bayberries, wax myrtles, candleberries or tallow shrubs 
(Cerothamnus), a group of about nine shrubs or small trees producing 
berries from which wax may be tried out by boiling in water. The best 
known member of this group in America is the wax myrtle or candleberry 
(M. cerifera L.). This is a shrub or small tree common along the Atlantic 
coast from New Jersey to Florida and the Gulf coast, also in sandy barrens 
of the interior. It is the common source of bayberry wax. It is said to be 
the cause of winter hayfever in Bermuda, together with Bermuda cedar 
(GAY, CURTIS and NORRIS 1941), and has been suspected in Florida. 
The small waxberry or bayberry (M. carolinensis Small) is a smaller form 
occurring along the coast from Nova Scotia to Florida, around the Great 
Lakes and elsewhere in the interior. It is the common form along the 
Massachusetts coast where it is still used for making candle wax. On the 
Pacific coast is still another member of this group, the California wax 
myrtle (M. calijornica Cham.) extending in distribution from southern 
California to British Columbia, reaching its best development in the region 
of San Francisco Bay. (3) The sweet fern (Comptonia perigrina Coult), 
a small shrub with fragrant aromatic fern-like leaves in dry sandy or rocky 
soils almost throughout North America. 

All of these shed large quantities of pollen which possesses the physical 
characteristics of hayfever pollen. Their role in hayfever is not fully un- 
derstood and is further confused by the fact that their pollen grains when 
caught on pollen slides are scarcely to be distinguished from those of the 

Ulmaceae (The Elms and Hackberries) 

The elm family comprises about 13 genera and 140 species of trees and 
shrubs of wide distribution. Five genera are represented in North America. 

Chapter III 



All are wind pollinated and apparently capable of causing hayfever. Be- 
sides the three genera discussed below two species of nettle trees (Trema 
Lour.) are found in Florida, and two chaparral trees (Momisia Dietr.) in 
the South from Florida to Texas. 

The affinities of the family are not clear. It was formerly regarded as a subdivision 
of the nettle family (Urticaceae) . Now it is regarded as a separate family but treated 
as a member of the order Ur tic ales which includes, besides the elm family, the mul- 
berry, hemp and nettle families. Apparently all members of this order are wind polli- 
nated. Consequently both their floral structures and their pollen grains are so far 
reduced that their relationships are largely obscured. 

Ulmus and Planera (The Elms) 

The elms comprise 18 or 20 species, mostly trees with deeply furrowed 
bark. They are widely distributed throughout boreal and temperate regions 
of the northern hemisphere, but in America are confined to the region east 

FIG. 41. White elm (Ulmus americana), flowering twig. 

of the Rocky Mountains. Their flowers are small and inconspicuous but 
perfect, possessing both stamens and pistils. They open either very early, 
long before the unfolding of the leaves, as do the northern elms, or in the 
late summer or even in the fall, as do some of the southern elms. They 
shed large amounts of pollen of high allergenic toxicity. 

Their pollen grains (fig. 40 F) are oblately flattened, 29 to 43/x in 
diameter, somewhat angular in outline, provided with four to six pores 
(generally five except in U. julva in which there are generally four). The 
pores are elliptical, about 5ju long and arranged around the equator with 
their long axes biconvergent. The exine is rather thick and thrown into 
conspicuous ripple-like thickenings, and generally thicker around the pores. 
The grains of the water elm (Planera) are the same as those of the elms 
except that there are two band-like thickenings reaching from pore to pore 

Roger P. Wodehouse 


Hayfever Plants 

n sweeping curves, one on each side of the equator, similar in this respect 
o the grains of the alders. 

The commonest species is the white elm (U. americana L., fig. 41), a 
all graceful tree reaching a height of more than 100 feet, one of the most 
>eautiful trees of our native flora. It is common almost throughout North 
\merica east of the Rocky Mountains. It flowers very early, generally 
n March or April, or earlier in the South. The flowers are so small and 
nconspicuous that they can scarcely be seen from the ground, though they 
;hed prodigious quantities of pollen. Somewhat similar, though less grace- 
ul and smaller, is the slippery elm (U. julva Michx., fig. 42). Its flowers 

FIG. 42. Slippery elm (Ulmus julva}, flowering twig. 

ire borne on short pedicels in crowded capitate fascicles. In the north- 
astern states is also found the cork or rock elm (U. racemosa Thomas), 
t may be distinguished from the two preceding species by having corky 
vings on its twigs and branches. 

In the southeastern states are found several species of early flowering 
1ms similar to those of the North. The wahoo or winged elm (U. data 
tfichx.), characterized by corky wings on its branches, is common from 
/irginia to Florida and westward to Illinois and Texas. It is also called 
ed, cork and water elm in allusion to the characters of its bark and its 
labit of growing in wet places. It flowers in early spring before the opening 
>f its leaves. The Florida elm (U. floridana Chapm.) is a small tree with 

Chapter III 89 Angiosperms 

smooth twigs lacking corky wings, in swamps and low hammocks of the 
Coastal Plane region from Florida to North Carolina. 

Remarkable among the native southern elms are two late flowering 
species. The cedar or scrub elm ( U. crassifolia Nutt. ) is a small tree with 
downy twigs, more or less corky winged, and leaves thick and leathery at 
maturity. It is common from Mississippi to Texas and Arkansas. Its 
flowers open generally in August or even as late as October. The Septem- 
ber or red elm (U. serotina Sarg.) is a small tree with downy twigs and 
corky-winged branches. It is common in Georgia, Alabama and Tennessee 
where it is occasionally planted as a street tree in cities. It flowers in 
September. These two late flowering species are known to cause some 
hayfever, especially the former, and serve to complicate the problem of late 
summer hayfever in the South. 

Besides the native species, the English elm (U. campestris L.) has been introduced 
and is common in New England, and the Scotch elm (U. glabra Huds.) is found in 
the north Atlantic States. The Chinese dwarf elm (U. pumila L.) is planted in dry 
regions as a wind break and has been proved by recent shelter belt experiments at 
Mandan, North Dakota (GEORGE 1936), to offer the highest resistance to the rigors of 
that climate. 

Geltis (The Hackberries or Nettle trees) 

The hackberries are shrubs or small trees with smooth or warty bark. 
They are wind pollinated, the flowers perfect or monoecious, appearing in 
the spring at the time of the unfolding of the leaves. Their fruits which are 
berry-like ripen toward the end of summer. 

The genus comprises about 50 or 60 species widely distributed in both temperate 
and tropical regions, about 8 in North America. It appears that the two commonest 
species may cause some hayfever. The one generally mentioned in hayfever literature 
is the common hackberry or sugarberry (C. occidcntalis L.) also called false elm, 
beaver wood, hoop ash. It is a small tree with ovate pointed leaves and dark purple 
fruits, fairly common generally in dry rocky soil from Quebec to North Carolina and 
westward to Manitoba and Missouri. 

The pollen grains (fig. 40E) of this species are extremely various; 
they range in size from about 30 to 65/x in diameter and are provided with 
roundish germ pores varying in number from 3 to 10 and in size from 3 to 
7/x in diameter, and are scattered over the surface without any system of 
arrangement. Each is surrounded by a weakly developed shield-like thick- 
ening or occasionally, if very close, two or more sharing the same shield-like 
thickening. The exine is smooth or slightly warty-granular. 

A similar species is the southern hackberry (C. laevigata K. Koch, 
C. mississippiensis Spach) but which may be distinguished by its narrow 
pointed leaves and orange-red or yellow fruits ripening in September. It 
is usually a fair-sized tree, reaching sometimes 60 feet in height, in dry 
soil from Virginia to Florida and westward to southern Illinois and Texas. 
It flowers in April just as the leaves unfold. 

The importance of the hackberries in hayfever appears to be not well understood. 
They are generally included in lists of hayfever plants or of those with hayfever possi- 
bilities as, for example, DUKE (1926). SCHEPPEGRELL (1922) states that hackberry 
pollen gives reactions with hayfever patients and THOMMEN (1931) states that the most 

Roger P. Wodehouse 90 Hayfever Plants 

important hackberry in hayfever is C. occidentalis. Tala (Celtis Tola) is reported to be 
an important cause of hayfever in Argentina (WALKER and CARRON 1940, CARR6N and 
MALVAREZ 1941). WALKER and CARR6N say it sheds as much pollen as ragweed does 
in the United States. It is a tree or shrub widely distributed in the central part of 
Argentina, flowering from September to December. "This pollen was found to be the 
chief offender in 44 per cent of patients with hayfever." 

Moraceae or Artocarpaceae (The Mulberry Family) 

The family comprises about 54 genera and 1000 species of monoecious 
trees or shrubs widely distributed but principally tropical. Four genera 
are represented in the United States, Morus, Madura and Ficus native, and 
Broussonetia by introduction from Asia. It appears that the American 
species, except Ficus, are wind pollinated and capable of causing very severe 
hayfever though cases are relatively infrequent. The relationships between 
the three following genera appear to be so close that sensitization to the 
pollen of one implies sensitization to that of the others (BERNTON 1928). 

Morus (The Mulberries) 

The mulberries are trees or shrubs, monoecious or dioecious with the staminate 
and pistillate flowers on different branches of the same tree or on different trees, minute, 
the staminate in elongate cylindric spikes. Each flower has four stamens bent inward 
in the bud but straightening elastically and becoming exserted at maturity, shedding 
large amounts of pollen which is occasionally the cause of hayfever. 

The pollen grains (fig. 45B) are ellipsoidal or spheroidal, about 20^ in diameter, 
with generally two, occasionally three, germ pores which are not placed diametrically 
opposite. The pores are circular, about 3.5^ in diameter, their membranes bulging 
when the grains are expanded, and capped with a thickening of exine-like material. 
The exine is thin and smooth or slightly granular. These grains are similar to those 
of the nettles and paper mulberries but may be distinguished by their larger size. 

The genus comprises about 10 species. Only two are native of North America but 
several others have been introduced. Of the native species the red mulberry (M. rubra 
L.) is a medium sized tree attaining a maximum height of 65 feet. It flowers in April 
or May and its dark purple red fruit which has a delicious flavor ripens in June or 
July. It occurs in rich soil in the eastern United States from Vermont to Florida and 
westward to South Dakota and Texas. The white mulberry (M. alba L.) is native of 
China where it is grown for feeding silk worms. It is also widely cultivated in the 
United States and Canada occurring in fruit-bearing and ornamental varieties. In its 
natural form it is a medium sized tree. It flowers in May and bears pink or whitish 
fruits in July or August. It is sparingly escaped from cultivation in Maine and On- 
tario and southward to Florida. 

The paper mulberry (Broussonetia papyrtfera Vent., Papyrius papyri- 
fera Ktze.), though not a true mulberry, is closely related to the mulberries 
and its pollen appears to interreact almost perfectly. It is a small to medium- 
sized tree, wind pollinated, the pistillate flowers borne in dense globular 
clusters and the staminate in catkin-like spikes. The flowers have the 
remarkable habit of forcibly ejecting their pollen. Apparently there is 
some synchronizing mechanism enabling many flowers on the same branch 
to release their pollen at the same time so that the branches appear to give 
off periodically puffs of smoke. Its pollen grains (fig. 45E) are similar 
to those of mulberry but smaller (13.4/1, in diameter). It has been shown 
by BERNTON (1928) to be a potent cause of hayfever. 

Chapter III 91 Angiosperms 

The paper mulberry is native of China and Japan but extensively cultivated as an 
ornamental in warm climates elsewhere. In the United States it is thoroughly natural- 
ized throughout the Southeast and as far north as Pennsylvania and west to Oklahoma 
and Texas. Of it BALYEAT and RINKEL (1932), who have made an exhaustive study 
of the American distribution of this plant, and the part it plays in hayfever, state that 
in the southwestern part of Oklahoma it is cultivated for shade in practically every 
village and city. These authors also furnish a map showing the relative abundance 
of the tree in the various states of the Southwest. It flowers during the latter part of 
April or in May. 

Osage Orange (Madura pomifera Schneid., Toxylon pomiferum Raf.) also called 
mock orange or bow-wood, is a tree 50 to 60 feet high, bearing pistillate flowers in 
dense globular clusters and staminate in short loose racemes in June. The fruit which 
is a large greenish-yellow syncarp about the size of an orange ripens in the autumn. 
It is most abundant in southern Arkansas to southern Oklahoma and southward in 
Texas but it is also planted as a hedge plant in the prairie regions of the Mississippi 
River basin, and in the eastern states. 

Its pollen grains (fig. 4SC) are oblate spheroidal, smooth, about 19.5 x 22/* provided 
with 3 or, occasionally, 4 or 2 germ pores which are small and surrounded by a sub- 
exineous thickening, and with their membranes provided with a central thickening. 
These grains are similar to those of Mulberry except that they are prevailingly three- 
pored. This pollen appears to interreact more or less perfectly with that of the paper 
mulberry, and is occasionally a serious cause of hayfever. 

Gannabinaceae (The Family of Hemp and Hop) 

This family comprises only the hemp and hop. They are herbaceous 
annuals or perennials with dioecious flowers, entirely wind pollinated. The 
staminate are borne in panicled racemes, the pistillate in bracted spikes. 
Both species shed large quantities of extremely buoyant pollen. 

The hemp (Cannabis sativa L.) is an annual coarse herb with palmately 
divided leaves, and topped by long spikes of staminate flowers opening from 
July to September. It is native of Asia but introduced into the United 
States as a source of fibers which are made into cordage, and as a source 
of the narcotic drugs marijuana and hashish. It is now extensively escaped 
in waste places throughout the northeastern states as far south as Georgia 
and westward to Kansas and Minnesota. 

The pollen grains of hemp (fig. 45 D) are oblate spheroidal, about 25ft 
in diameter, with generally three germ pores, occasionally two or four, 
each surrounded by a subexineous thickening and slightly protruding. 
Their exine is thin and smooth. 

Hemp is undoubtedly an important cause of hayfever in regions where 
it is abundant. DURHAM (1933d) states that at various places along the 
Mississippi and Missouri rivers there are areas in which hemp is more com- 
mon than ragweed, but Omaha is the only place investigated where it was 
found to assume allergenic importance. MALONEY and BROADKEY (1940) 
confirm this observation and state that since hemp was introduced into 
Nebraska in 1889 it has grown wild all over the state, its pollen constituting 
17 per cent of the pollen in the air over Omaha during late summer and 
fall, and 22 per cent of their hayfever cases there were found to be sensi- 
tive to it. 

Eloger P. Wodehouse 92 Hayfever Plants 

Government regulations prevent the use of hemp pollen, except with 
ill the inhibitions imposed by the narcotic laws, though it is doubtful if an 
ippreciable quantity of narcotic is contained in it. 

The hop (Humulus Lupulus L.) is a perennial vine. It flowers in July 
md August. Its staminate flowers are borne in panicled tassel-like racemes 
ind the pistillate in pendent cones forming at maturity the familiar hops 
)f commerce. It is native of Europe but cultivated in hop yards and for 
)rnament in America, and is extensively escaped throughout much of the 
Jnited States and Canada east of the Rocky Mountains. Its pollen grains 
ire indistinguishable in appearance from those of hemp. Their role in 
layfever is not fully understood. 

Polygonaceae (The Buckwheat Family) 

The buckwheat family is a large and diversified group comprising about 
1O genera and 800 species of herbs, vines and trees. They are all charac- 
erized by having jointed stems, usually wrapped at the nodes by united 
ind sheathing stipules. Included in this family are such familiar garden 
)lants as prince's feather (Polygonum orientate L.), buckwheat (Fagopy- 
'iim esculentum Moench) and rhubarb (Rheum Rhaponticum L.). Most 
ire herbaceous but the sea grape and pigeon plum of Florida and the 
Bahamas are small trees. By far the majority are entirely insect pollinated 
ind of little interest to the student of hayfever. The docks and rhubarb, 
lowever, are exceptional in being entirely wind pollinated. The docks are 
generally recognized as hayfever plants but, as far as I am aware, rhubarb 
las never been shown to cause hayfever. 

The pollen grains of the Polygonaceae are extremely various among the 
intomophilous species, and some of them, such as those of the knotweeds 
(Polygonum, Persicaria, Tracaulon and their relatives) are elaborately 
;culptured and strikingly beautiful, but those of the anemophilous members, 
he docks, rhubarb and Muehlenbeckia are plain, almost entirely lacking 
n sculpturing. 

Rumex (The Docks) 

The genus comprises about 140 species of leafy stemmed annual or per- 
ennial herbs. About 35 are native or naturalized in the United States. 
Their pollen grains (fig. 45F) are spheroidal when moist and expanded, 
)rovided with three to six (generally three or four) linear furrows arranged 
ather strictly according to the trischistoclasic system, each provided with 
i small elliptical germ pore, and with an exine thin and finely pitted. 

Though some docks shed rather large quantities of pollen which is light 
md easily dispersed by wind, they are relatively unimportant in hayfever. 
The one generally mentioned in hayfever literature is the sorrel dock 
(R. Acctosella L., fig. 43) also called field, red, wood and sheep sorrel. It 
s a low perennial herb with fleshy hastate or halberd-shaped leaves with 
in acrid taste, and dioecious reddish or yellowish flowers which shed large 
juantities of pollen throughout most of the summer but mostly in May or 
iarly June. It is a common weed in dry fields and waste places, particularly 

Chapter III 



where the soil is impoverished and acid. It occurs practically throughout 
North America though it is not native, having been introduced from Europe. 
Two other species which are fully as common and widely distributed as 
the sorrel dock are the curly dock (R. crispus L., fig. 44) and the broad- 
leaved or bitter dock (R. obtusifolius L.). Both are tall leafy-stemmed 
perennials, quite different in appearance from the low fleshy sorrel dock, 
but so similar to each other that it is not always easy to tell them apart, and 

FIG. 43. Sorrel dock (Rumcx Acetosclla}. 

this difficulty is further increased by the occurrence of natural hybrids 
between them. Generally, however, curly dock may be recognized by its 
narrower leaves with curled margins, and the broad-leaved dock by its 
broader leaves and the laciniate margins of its calyx wings. Both are 
adventive from Europe and are now spread almost throughout North 
America. They flower from June to August, but shed much less pollen 
than the sorrel dock. 

Roger P. Wodehouse 


Hayfever Plants 

In the western part of the United States occurs another species, the 
canaigre (R. hymenosepalus Torr.) which is believed to occasionally cause 
hayfever. It is a coarse perennial herb growing naturally in dry sandy 
washes from California eastward to New Mexico. It is also cultivated for 

FIG. 44. Curly dock (Rumex crispus}. 

its large fleshy dahlia-like roots which are used for tanning leather, and 
its juicy stem which is used as a substitute for rhubarb. As a consequence 
of these uses it is sometimes known in these regions as pie or sour dock, 
and wild rhubarb. 

Chapter III 



Amaranthaceae (The Family of the Pigweeds and Waterhemps) 

The amaranth family comprises about 40 genera and 475 species, for 
the most part weedy herbs, though some exotic genera are low or climbing 

FIG. 45. POLLEN GRAINS : A, Sweet gale (Myrica Gale} ; B, Mulberry (Morus) ; 
C, Osage orange (Madura pomifera} ; D, Hemp (Cannabis saliva} ; E, Paper mul- 
berry (Broussonetia papyrifera} F, Dock (Rumex) ; G, Russian thistle (Salsola 
Pestifer} ; H, Wingscale (Atriplex canescens} ; I, Greasewood (Sarcobatus vermic- 
ulatus) ; J, Pigweed (Amaranthus retroflexus) ; K, Sweet gum ( Liquid ambar styraci- 
flua}. All magnified 1300 times. 

loger P. Wodehouse 96 Hayfever Plants 

hrubs. Some species are wind pollinated, others insect pollinated, but the 
lowers of all are characterized by extreme simplicity, exhibiting the kind of 
eduction which comes about through adaptation to wind pollination. The 
lowers may be perfect or, less frequently, monoecious or dioecious, but they 
re always small, often greenish or yellowish, and the corolla always entirely 
acking. They may have a calyx of two to five sepals but this is nearly 
Iways greenish and inconspicuous. Each flower is accompanied by gen- 
rally three scarious bracts. They are variously clustered, occasionally in 
:>ng slender open spikes, but more generally in dense terminal spikes or 
ompact axillary heads. In most species the inflorescences are green or 
traw colored, as among the amaranths and waterhemps, but in some they 
re white or highly colored and showy, as in the cultivated cockscomb 
Celosia) and the globe amaranth (Gomphrena). The stamens vary in 
lumber from three to five. In the amaranths and waterhemps they are 
ntirely separate, but in others their filaments are more or less united, and 
n some, as for example the globe amaranth, they are united into a long 
taminal tube forming a sort of substitute corolla. 

Apparently anemophily is the primitive condition in this family and entomophily, 
ccurring in the cockscomb and globe amaranth, secondarily acquired. Though nine 
r ten genera are represented by native species in America only the amaranths and 
waterhemps are important in hayfever ; the others are either too scarce or shed too 
ttle pollen. The amaranths and waterhemps are entirely wind pollinated and some 
f their species shed huge quantities of pollen which causes much hayfever. The globe 
maranth, cockscomb and probably most of the cultivated forms appear to be entirely 
isect pollinated, as suggested by their brilliantly colored flower heads, which are ob- 
srved to be freely visited by bees. 

The pollen grains of most anemophilous species are spheroidal, 25 to 
5/x in diameter, provided with rather numerous germ pores, ranging in 
ize from 2 to 4.5/* in diameter and arranged at least partly according to 
tie trischistoclasic system. The pore membranes are flecked with granules 
/hich are variously distributed but do not tend to aggregate at the center, 
lie exine is thin and more or less granular (fig. 45J). These grains can 
carcely be distinguished from those of the Chenopod family, but those of 
he different species differ from each other in their size and in the size and 
listance apart of the germ pores. 

It has been shown by LAMSON (1931) and by SELLERS and ADAMSON 
1932) that the pollens of various species of this family interreact almost 
erfectly with each other and with those of the related Chenopodiaceac, 
howing only slight allergenic differences in some cases. 

Amaranthus (The Amaranths or Pigweeds) 

The amaranths are annual herbs, usually coarse and weedy though some, 
uch as the princes-feather, which is a variety of the spleen amaranth 
A. hybridus L.), and the tassel amaranth (A. paniculatus L.), are culti- 
ated for their red or otherwise highly colored panicles and foliage. The 
lowers are generally monoecious or dioecious but may be bisexual. The 
tamens are commonly five, occasionally two or three, with their filaments 
ntirely separate. In this latter character they are like the waterhemps 

Chapter III 



but unlike most other members of the family. Their flowers are always 
small and inconspicuous, closely aggregated into dense chaffy spikes or 
panicles, and virtually hidden from view by their subtending bracts. 

The genus comprises about 50 species of which about 35 are native of 
North America and include some of our most important weeds. The weed 
species appear to be all immigrants to the United States from tropical 
America. The best known and most ubiquitous of the group is the common 

FIG. 46. Carelessweed (Atnaranthus Paltneri). 

or red-root pigweed (A. retroflexus L., fig. 47), also called green amaranth. 
It is a rough coarse weed from one to ten feet high, with its flowers densely 
aggregated into thick terminal or axillary spikes. It is common in culti- 
vated or waste soil throughout North America, also in Europe. The flow- 
ers shed surprisingly little pollen but in regions where the plants are most 
abundant it probably causes some hayfever during the latter part of summer. 
Often associated with the red-root pigweed but less common, is the 

loger P. Wodehouse 98 Hayfever Plants 

pleen amaranth (A. hybridus L.). It may be distinguished by its darker 
olor, reddish stem and often deep red panicles which are long, slender and 
requently drooping. Also similar is the carelessweed (A. Palmeri Wats., 

FIG. 47. Pigweed (Amaranthus retro flexus}. 

[g. 46). It may be distinguished by its long slender terminal flowering 
pikes and the longer petioles of its leaves. It flowers from June to Sep- 
ember, shedding much more pollen than the red-root pigweed, and in the 
egion of Missouri, Kansas, Oklahoma and eastern Texas where it is most 

Chapter III 



abundant, is believed to be important in hayfever. The spiny amaranth 
(A. spinosus L.) is somewhat similar but monoecious with the staminate 
flowers in long slender spikes and the pistillate in globular clusters in the 
axils of the leaves. The leaves are rhombic-ovate or ovate-lanceolate with 
a pair of spines in their axils. The spiny amaranth occurs in waste ground 
from Maine to Minnesota and southward. In the western and southern 
parts of its range, where it is most abundant, it occasionally appears to be 
an important factor in hayfever. 


FIG. 48. Western waterhemp (Acnida tamariscina) . 

Acnida (The Waterhemps) 

The waterhemps are similar in appearance and habit to the amaranths 
but are always dioecious. The calyx of the staminate flowers consist of five 
thin mucronate sepals longer than the bracts, the pistillate flowers are 
without calyx. The genus comprises six species native of North America 
and the West Indies, 

Roger P. Wodehouse 100 Hay fever Plants 

The western waterhemp (A. tamariscina Wood, fig. 48) is abundant in 
the prairie region from South Dakota through eastern Nebraska and Kansas 
to the northeastern corner of New Mexico and south through the eastern 
half of Texas, and eastward to Indiana. It reaches its maximum abundance 
in Oklahoma where BALYEAT and STEMEN (1927) find that it is one of the 
most important causes of late-summer hay fever, the sole cause of 3.6 per 
cent, and a definite contributing factor in 35 per cent of such cases. They 
also regard it as "a very important factor in hay fever in the eastern half 
of Nebraska, the eastern third of South Dakota, many sections of Iowa, 
some in Illinois, and part of southern Indiana". 

A. tubercuhta Moq. (A. altissima Ridd.) is of similar appearance and habit but 
the two species may be distinguished by the way in which the fruit, which is a small 
bladdery utricle, opens ; in A. tamariscina it dehisces by a regular transverse circular 
line of division but in A. tuberculata it dehisces irregularly. The latter species is less 
widely distributed, but is abundant in the eastern part of the Dakotas, in Minnesota and 
Iowa, also in Vermont. Its role in hayfever appears to be not fully understood. Of it 
BALYEAT and STEMEN say, "Since A. tuberculata is so closely related to A. tamariscina, 
botanically, it surely must be a factor in the cause of hayfever in districts where it is 
prevalent. Therefore it is quite probably a factor in many sections of Iowa, southern 
Wisconsin and eastern North Dakota". 

The pollen grains of western waterhemp are somewhat various in size, 
normally 21 to 28.5//, in diameter, their pores 2 to 2.8/x in diameter and 3 to 
4.6/A apart, their membranes flecked with granules which tend to aggregate 
toward the center and fuse together. 

Cladothrix (Tidestromia lanuginosa Standl., Cladothrix lanuginosa Nutt.) is an 
annual with clusters of white fuzzy stems, seldom over 16 inches high, and small round- 
ish leaves. It forms conspicuous whitish mats and is a common weed in the high 
plains, waste places and disturbed areas, western Kansas to Utah, south to northern 

It has not been shown to cause hayfever, but is wind pollinated and appears to 
have all the characteristics of a hayfever plant. Its pollen grains are somewhat aber- 
rant for the family, 17. IM in diameter, the surface marked off by ridges dividing it into 
12 equal pentagonal faces, corresponding to those of a pentagonal dodecahedron, with 
a pore on each face, their membranes flecked and their margins jagged (illustration 
WODEHOUSE 1942b). 

Chenopodiaceae (The Chenopods or Goosefoots and Saltbushes) 

The goosefoot family is closely related to the amaranth family, though 
not generally similar in appearance. They are mostly fleshy annual or 
perennial herbs, occasionally shrubs, often succulent and glaucous. Their 
leaves are alternate, simple, and without stipules. Their flowers are small, 
inconspicuous and generally greenish ; they may be perfect, monoecious or 
dioecious, but they appear to be always wind pollinated; they are entirely 
without a corolla but generally have a calyx of three to five herbaceous 
sepals though even this may be absent in the pistillate flowers of some 
genera; they are variously clustered, commonly in panicled spikes, with 
or without bracts which, when present, are never scarious as in the amaranth 

The pollen grains of all species are much alike and essentially the same 
as those of the anemophilous Amaranthaceae. They are spheroidal, 19 to 

Chapter III 101 Angiosperms 

33/x in diameter. The exine is thin and conspicuously granular, provided 
with round germ pores. These are various in size and number in the 
different species, and in this are occasionally of diagnostic value. Each is 
covered by a delicate membrane which is always more or less flecked with 
granules which tend to be aggregated toward their centers, a circumstance 
which occasionally serves to distinguish these grains from those of the 

The family comprises about 75 genera and 550 species of world-wide distribution. 
Some species shed large quantities of pollen which is undoubtedly a serious cause of 
hayfever, but most appear to be quite harmless, either because they are not abundant 
enough or because they shed too little pollen. Most of the troublesome species are 
introduced weeds of waste places, and of no economic value for they are generally not 
eaten by stock. As other vegetation is destroyed by over grazing and faulty agriculture 
many of the Chenopodiaceae take over the territory and so are gaining in abundance. 
On the other hand, two species of the family are of great economic importance. The 
beet (Beta imlgaris L.), a native European species which includes such valuable crop 
varieties as the sugar beets, mangels and Swiss chard, is widely cultivated in America. 
It produces greenish or reddish flowers in late summer or fall. The sugar beet appears 
likely to become an important cause of hayfever in America. BUTTON (1938) reports 
that beet hayfever is rapidly becoming a major problem in the Mesilla valley of south- 
ern New Mexico and western Texas. Severe attacks are suffered by patients from 
beet pollen encountered by merely driving through the irrigated sections of the valley 
where the beets are grown, and from the dust that is scattered from threshing the seed. 
According to PHILLIPS (1939) it already is important in Arizona. Beet-sugar industry 
has recently been introduced into this state, stimulated by a protective tariff. Since 
1936 the acreage devoted to it has increased from 1800 to 5500 acres in 1939. PHILLIPS 
states that in April and May when the plants bloom they are three to six feet high 
and look like hedges, and have a sickening sweetish perfume. Pollen production is 
enormous. "Individuals clinically sensitive to the pollens of other chenopods were 
found especially liable to acquire sensitivity to beet pollen, but the treatment that 
protected them against the pollens of amaranth and Russian thistle did not prove a 
defense against sugar beet pollen. The sugar beet has, in addition to the group atopen 
common to the Chenopodiales, a potent atopen of its own". Beet pollen grains are 
about 19.4/u in diameter with pores 2.75M in diameter and 5.6/t apart. 

Similar and closely related to beet is spinach (Spinacea olcracea L.). It is domes- 
ticated in America from the Old World where it has been cultivated as a pot herb from 
prehistoric times. It flowers throughout most of the summer, producing a fair amount 
of pollen which has hayfever possibilities but is not considered important. Its pollen 
grains are about 30/* in diameter with pores about 6.5/* in diameter and 2.3M apart. 

Among our native species several common weeds of the western prairies and deserts 
have the appearance of being hayfever plants. The winged pigweed or tumbleweed 
(Cycloloma atriplicifolium Coult. ) is common along streams and river banks through- 
out the central part of the United States from the Mississippi River to the Rocky 
Mountains. It flowers during most of the summer. The monolepis or poverty weed 
(Monolepis Nuttalliana Engelm.) is a low branching annual weed common in alkaline 
and dry soil throughout the prairie region of the central part of the United States, 
flowering from June to September. Winter fat (Eurotia \a\iaia Moq.) also called white 
or sweet sage is found in dry soil, often in desert valleys, throughout the Rocky Moun- 
tain region and adjoining plains. The plant is densely silky throughout and forms dense 
silvery clusters which are conspicuous objects in the plains and table lands of the 
Rocky Mountains. It flowers from June to September but, though wind pollinated, 
produces so little pollen that it is probably not important in hayfever. The burroweed 
(Allenrolfia occidcntalis Ktz., Spirostachys occidentalis Wats.), also called iodine bush 
or pickleweed, is entirely different ; its stems are smooth and succulent, almost glassy 
in appearance, and its leaves reduced to scales which are tightly appressed against the 
stems, only gaping apart slightly to allow the anthers of the enclosed flowers to protrude 

Roger P. Wodehouse 102 Hayfever Plants 

as they shed their pollen. The pollen grains are about 20.4/i in diameter, with pores 
about 5.1M in diameter and 2.8^ apart. The plant is common in salt marshes in Utah, 
Arizona and southern California, being particularly abundant along irrigation ditches. 
It flowers from July to September shedding enormous quantities of pollen. 

A similar plant, both in its succulent form and in its adaptation to saline situa- 
tions, is the glasswort or samphire (Salicornia ambigua Michx.). It is a low herb with 
thick jointed leafless stems and opposite branches. The small flowers are sunken in 
the upper fleshy thickened joints, forming spikes. It is common along both the Pacific 
and Atlantic coasts. Flowering from May to September, it produces relatively little 
pollen and is probably of no importance in hayfever. But ROWE and HOWE (1935) in 
their discussion of the hayfever plants of northwestern California say, "The marshes 
which bound the inlets and embayments yield large amounts of Salicornia pollen". In 
the West are also several species of Dondia or Sueda, known as seablites, alkaliblites 
or seepweed. These are fleshy plants of salt marshes or alkaline plains of California 
and the Southwest, with something the habit of Russian thistle. Dondia Moquini A. 
Nels is an especially common weed of the Southwest (PIEMEISEL and LAWSON 1937, 
SHANTZ and PIEMEISEL 1924) . They shed a good deal of pollen in mid and late summer 
which has hayfever possibilities. HALL (1922) lists >. fruticosa Druce among the 
more important hayfever plants of California, and its pollen was shown by PINESS to 
give reactions with hayfever patients. 

The greasewood or chico (Sarcobatus vermiculatus Torr.) is an erect shrub one 
to three feet high with spinescent tangled and matted branches. Its flowers are monoe- 
cious or dioecious, the staminate borne in erect catkin-like spikes. It is abundant in 
dry and saline soils and alkaline flats throughout the Rocky Mountain region south of 
Montana. It flowers from June to July shedding large amounts of pollen. The grains 
(fig. 451) are 24 to 30/u, in diameter with pores 3^ in diameter and HM apart, these 
grains having the fewest pores of any so far encountered in this family. 

Much more important from the hayfever standpoint than any of the 
above are the two introduced species, Russian thistle and burning bush. 
Russian thistle (Salsola Pestifer A. Nels.), also known as tumbleweed or 
saltwort, is an annual herb with dryish spine-tipped leaves, divaricately 
branching, the branches matted together so that the whole plant resembles 
a gigantic sponge. Toward the end of summer as the plant dries up it 
breaks off at the root and is rolled about the plains by the wind, scattering its 
seeds as it goes, until arrested by a fence or some other obstruction in its 
path. Its flowers are small and inconspicuous, each shedding only a minute 
amount of pollen, but borne in prodigious numbers. Its pollen grains 
(fig. 45G) are about 27/x in diameter, with pores about 3.7//, in diameter, 
which is larger than usual for the family, and 6.6/x apart. Russian thistle 
has a range extending almost throughout the prairies, much of the Rocky 
Mountains, and the Great Basin area. It flowers from June to September 
and is probably the most important cause of hayfever among the Chenopo- 
diaceae. It was introduced into this country from Europe or Asia at a com- 
paratively recent date, probably less than a hundred years ago, and is still 
invading new territory. PIEMEISEL (1932) points out that "Russian thistle 
is the pioneer on bare lands'*. That is to say, when the land is broken and 
its native vegetation destroyed, Russian thistle is the first plant to repossess 
the area, which accounts for its enormous and rapid spread in recent years. 

Burning bush (Kochia scoparia Roth), also called fire bush, summer 
cypress, belvedere and kochia, is somewhat similar to Russian thistle but 
has longer leaves which are herbaceous and not spine tipped. It is a small 
and profusely branching annual forming a compact pyramidal bush. Its 

Chapter III 103 Angiosperms 

symmetrical form and the brilliant red color which its leaves assume toward 
the end of summer make it a popular plant in formal gardens. It is native 
of Europe and Asia, but in America has escaped from cultivation and 
become naturalized locally in fields and waste places in the northern United 
States. It sheds large quantities of pollen from July to September, and in 
Colorado where it is thoroughly naturalized and particularly abundant, it 
is counted among the worst hayfever weeds. Originally escaped from culti- 
vation and a common cause of hayfever only in Colorado, this plant is 
rapidly spreading eastward. It is now reported by DURHAM (1943) to 
be a factor of importance in the following states, named in the order of its 
abundance: Iowa, South Dakota, Wyoming, Colorado, Wisconsin, Min- 
nesota. Its pollen grains are 29 to 30/ut in diameter, with pores about 3/u 
in diameter and 6/x apart. Redsage (Kochia americana Wats.) is a native 
species somewhat similar but only 5 to 11 inches high, with whitish stems 
and silky leaves becoming smooth at maturity. It occurs in desert valleys 
from California to Colorado, and is occasionally mentioned as a possible 
cause of hayfever but its importance has not been established. 

Chenopodium (The Chenopods or Goosefoots) 

The chenopods are leafy annual or perennial herbs, often white-mealy. 
The flowers are small but perfect, sessile and bractless, generally tightly 
clustered into axillary or terminal panicled or compound spikes. Though 
entirely wind pollinated, they do not shed excessive amounts of pollen, but 
they sometimes make up for this by their abundance so that the pollen may 
occasionally be a real factor in hayfever. The grains are 25 to 30/x in 
diameter, provided with small pores, 1 to 2.5/u in diameter and 4 to 5.5/x 

The genus comprises about 60 species, about 20 in America, mostly weeds 
of world wide distribution. The best known and most frequently mentioned 
in hayfever literature is lambsquarters (C. album L.). It is a tall succulent 
herb more or less mealy throughout. It is native of Europe but now nat- 
uralized throughout North America. In regions where exceptionally abun- 
dant it should probably be considered a contributory factor in hayfever. The 
nettle-leaved goosefoot (C. murale L.) is similar in appearance to lambs- 
quarters but may be distinguished by its broader leaf with more sharply 
toothed margin. It also is widely distributed but generally much less abun- 
dant than lambsquarters. 

Jerusalem oak (C. Botrys L.) is strikingly different in appearance from the two 
preceding species. It is an erect annual herb, glandular pubescent and with strong dis- 
agreeable aromatic odor. The flowers are borne in numerous axillary panicles and the 
leaves are irregularly pinnately lobed giving them some resemblance in shape to those 
of some oaks. It is native of Europe and Asia, occasionally cultivated in America and 
locally established in the northern United States and Canada. It flowers from July 
to September and may be a factor in hayfever where abundant, particularly westward. 
Mexican tea (C. ambrosioides L., fig. 49) is similar to Jerusalem oak in its glandular 
leaves and disagreeable odor but differs in appearance; its leaves are generally ovate- 
oblong with their margins only undulate. It is introduced from tropical America, and 
abundantly naturalized throughout North America. It flowers from August to Oc- 
tober shedding a rather large amount of pollen. The grains are 22.8/* in diameter, 

Roger P. Wodehouse 


Hayfever Plants 

.heir pores 1.2ft in diameter and 3.8M apart, their membranes marked by a single central 

The oak-leaf goosefoot (C. glaucum L.) is a low spreading glaucous mealy an- 
lual herb with leaves sinuately pinnatifid-toothed, somewhat resembling Russian thistle, 
't is a European weed, here naturalized in sandy soil and waste places. It flowers in 
July and August shedding rather large amounts of pollen. It is regarded as an im- 
portant cause of hayfever in Salt Lake City (BARRETT 1934) and is abundant in the 
/icinity of Chicago. 

FIG. 49. Mexican tea (Chenopodium ambrosioides) . 

Atriplex (The Saltbushes and Orachs) 

The saltbushes are annual or perennial herbs and shrubs with alternate 
eaves, or the lower opposite, more or less scurfy pubescent. The flowers 
ire monoecious or dioecious, entirely wind pollinated, and inconspicuous, 
generally aggregated into small compact glomerules which may be axillary 
Dr, more often, in terminal spikes or panicles. The flowers of both sexes may 

Chapter III 105 Angiosperms 

be mixed in the same cluster but more often the staminate are confined to 
the upper axils or terminal inflorescences. 

The pollen grains (fig. 45H) are various in size, 20 to 27/x in diameter 
with many pores, 2 to 3/x in diameter and 4 to 5.7/m apart, their membranes 
flecked with several small granules which tend to be aggregated toward 
their centers, and sometimes completely fused. 

The genus comprises about 130 species of wide distribution. About 60 
are native or naturalized in America, occupying saline, arid and semiarid 
soils throughout the continent. According to the classification of HALL and 
CLEMENTS (1923) which is followed here, the species fall roughly into two 
groups, monoecious herbs and dioecious shrubs, which are treated as sub- 
genera. The herbaceous group is fairly represented by the gardenscale or 
garden orach (A. hortensis L.) also known as French spinach and culti- 
vated as a potherb (BABB 1939). It is a low herbaceous plant with cheno- 
podium-like leaves, of Old World origin but sporadically escaped from 
cultivation in America. The shrubby group is fairly represented by the 
desert holly or holly scale (A. hymenelytra Wats.). It is a compactly 
branching shrub of alkaline deserts of the Southwest. Its silvery white 
leaves and branches make it popular for Christmas decorations and for this 
purpose the plants are shipped east by car loads. The members of the 
shrubby group correspond to the old genus Obione, under which name some 
of them still occasionally appear in hayfever literature. 

Of the saltbushes HALL and CLEMENTS say, "The pollen has been found 
to be one of the causes of hayfever of the late summer type in the West. 
Preliminary studies indicate that all species of the group are potential causes 
of the malady, their relative importance depending more upon the abundance 
in which the plants grow than upon the specific properties of the different 
kinds. It does not follow, however, that an individual sensitive to one 
species is necessarily sensitive to all, since it is found that patients react 
differently to the pollen of the various species." Fortunately most of the 
species either do not produce enough pollen or are not abundant enough to 
be very important. But some of them are potent causes of hayfever. 

In the eastern United States the saltbushes may almost entirely be disregarded 
as factors in hayfever. It is true that several do occur in the East and are recorded 
in hayfever surveys. These are all small plants and belong to the herbaceous group. 
For example the sea-beach atriplex (A, arcnaria Nutt), a low herb found on sandy 
beaches from Maine to Florida, and the spearscale (A. patula L.), common everywhere 
in saline soils, salt marshes and alkali flats almost throughout North America (also in 
Europe, Asia and North Africa). The latter flowers from August to October but 
sheds pollen only sparingly. It is claimed by ROWE (1928) to be among the most im- 
portant hayfever plants in the San Francisco Bay region of California but there is 
no reason to believe that it is of any importance in the East. Occasionally encountered 
in the southeastern states is the redscale or red orach (A. rosca L.). Though occurring 
only sporadically in the East, it is extremely abundant throughout most of the western 
half of the United States, particularly along roadsides and in saline places, and accord- 
ing to HALL and CLEMENTS, it is a serious cause of hayfever in these regions. It is 
naturalized from the Old World but is now the most widely distributed of all the salt- 
bushes in America. It flowers from July to September but sheds relatively little pollen. 

Information on the role that the different species of saltbush play in 
hayfever is probably far from complete. The botany of the genus, however, 

Roger P. Wodehouse 106 Hayfever Plants 

has been thoroughly worked over by HALL and CLEMENTS (1923) and is 
presented by them in a logical and easily comprehended form, with notes on 
hayfever and profusely illustrated. It is mainly from this great work that 
the materials for this discussion are drawn. 

The Australian saltbush or fleshscale (A. semibaccata R. Br.) is a 
prostrate perennial herb becoming woody at the base, with long trailing 
stems which form dense mats. Its flowers are monoecious, the staminate 
in small terminal leafy-bracted glomerules, the pistillate solitary or in few- 
flowered clusters. It was introduced into the United States by the Cali- 
fornia Experiment Station in 1888 as a forage and hay plant for alkaline 
districts. It is now thoroughly established throughout much of the South- 
west, particularly in the alkaline soils of the San Joaquin and Imperial Val- 
leys and the coastal strip of southern California. Though essentially a 
halophyte, it readily finds its way along roadsides and in disturbed places. It 
flowers from June to September shedding large amounts of pollen which 
undoubtedly causes some hayfever. 

Silvery orach or silverscale (A. argentca Nutt.) is an erect annual herb, 
6 inches to 2 l / 2 feet high with monoecious flowers in axillary glomerules, 
the staminate and pistillate mixed but the former mostly toward the ends of 
the branches which often end in long spikes of purely staminate flowers. It 
is one of the most abundant and widely distributed species of the genus, 
occurring in alkaline soils of western United States and northern Mexico, 
including most of the Rocky Mountain and Great Basin areas. Occasionally 
the plants spread from their customary saline habitats and become weeds in 
fallow fields and disturbed places. The species is extremely variable 
occurring in several recognizable forms which are treated by many authors 
as distinct species, and occasionally may be encountered as such in hayfever 
literature. The most important are A. caput-medusae Eastwood, A. inner- 
vata Jep., A. Hillmani Standl., A. mohavensis Standl., A. nodosa Greene, 
A. Rydbergii Standl. and A. volutans A. Nels. These, however, are at best 
only varieties of A. argentea and are best treated as synonyms. According 
to HALL and CLEMENTS, however, two distinct subspecies can be recognized 
A. argentea typica (A. argentea Nutt.) and A. argentea expansa (A. ex- 
pansa Wats.). In the typical form the leaves are all more or less petioled, 
while in the expansa form they are all closely sessile. The typical form is 
found principally in the region west of Nevada, while the expansa form, 
which is sometimes known as fogweed, is found from California to Texas. 
Both flower from May to October, principally June and July, shedding 
large amounts of pollen which is a frequent cause of hayfever. 

The bractscale (A. bracteosa Wats.) is an annual herb, erect or more 
commonly prostrate and spreading to form dense mats from which erect 
stalks arise bearing monoecious flowers, the staminate arranged in naked 
panicles or spikes. It is common in alkali valleys of California from Sacra- 
mento valley south to Lower California, very abundant in the San Joaquin 
valley and on the coastal slope of southern California, rare east of the Sierra 
Nevada. HALL and CLEMENTS say of this, "It was originally a moderate 
halophyte of the distichlis zone especially, but in recent years it has become 

Chapter III 



the most characteristic weed of disturbed areas in the San Joaquin valley. It 
often covers fallow fields, roadsides, fenceways, etc. with a dense pure 
community. The flowers appear from April to October. ... It is of no 
value, as it is not eaten by stock, but it is of some importance as a cause of 

FIG. 50.- Annual saltbush (Atriplex Wrightii). 

A closely related species but differing in its more erect habit is the annual 
saltbush (A. Wrightii Wats., fig. 50). It is an annual herb 3 to 4 feet high 
with monoecious flowers, the staminate in reddish glomerules arranged in 
long naked terminal panicles. It grows in dense stands in alkaline soils in 
river valleys, often associated with carelessweed. It also occurs sparingly 

Roger P. Wodehouse 108 Hayfever Plants 

along roadsides and as a weed in cultivated fields in southern New Mexico, 
Arizona and adjoining Mexico. It flowers from June to November and is 
regarded by WATSON and KIBLER ( 1922) as one of the most important hay- 
fever weeds in southern Arizona. 

Even more important than the herbaceous saltbushes are some of the 
shrubby species on account of their larger size and the larger amount of 
pollen that they generally shed. The shrubby species are mostly dioecious, 
that is to say each bush produces either only staminate or pistillate flowers, 
but a few species like A. lentijormis, are both monoecious and dioecious. 
They are more highly advanced than the herbaceous species in their adapta- 
tion to anemophily and generally shed much more pollen. 

Perhaps the best known and most important of the shrubby saltbushes 
is the wingscale or four-winged saltbush (A. canescens Nutt). This is the 
one which is generally spoken of in hayfever literature as "Shadscale". The 
name is a misnomer since it rightfully belongs to A. conjertijolia of which it 
aptly describes the pistillate inflorescence. Wingscale is a densely branched 
shrub, woody throughout, reaching a height of about eight feet, with gray 
scurfy leaves and twigs, the larger branches dark gray and exfoliating. The 
staminate glomerules are in dense spikes or long terminal panicles which are 
leafy below. The species is extremely various and many varieties have re- 
ceived specific names. It is by far the most widely distributed shrubby 
species of the genus, occurring from Alberta to Kansas, western Texas, 
Mexico, Lower California, Washington and Montana. According to HALL 
and CLEMENTS, "While its original role was evidently a consociation of the 
Basin sagebrush association, it occurs in the mixed prairie of the western 
Dakotas and Nebraska, the desert plains and desert scrub of the Southwest, 
and in the coastal sagebrush of California". It flowers from early spring to 
late summer shedding large amounts of pollen which has been shown to be 

A similar species is the allscale, desert sage (A. polycarpa Wats.). It 
is an erect shrub, woody throughout, 2 l / 2 to 6 feet high. The staminate 
glomerules are borne in axillary and terminal spikes, the pistillate crowded 
along the numerous divergent branches. It is characteristic of alkali basins 
in desert areas from southern Nevada, southern Utah, Arizona, adjoining 
Mexico and southern California, and is particularly abundant in the Mohave 
and Colorado deserts of western Arizona and eastern California where it is 
often associated with A. canescens and A. lentijormis, being only slightly 
less tolerant of alkali than the latter. It flowers from June to September. 
Its pollen has been shown to be allergenic and is believed to be an important 
cause of hayfever in the arid Southwest. 

Lenscale (A. lentijormis Wats.), also called quailbrush and silver-and- 
gold saltbush, is an erect woody shrub, 3 to 9 feet high and nearly twice 
as broad, with spiny branches. It is typically an intense halophyte. Accord- 
ing to HALL and CLEMENTS, "Its tolerance of alkali is greater than that of 
any other plant investigated, and this is in accordance with its dominance 
in the most alkaline habitats of the Southwest". It is found from the south- 
ern half of California to Nevada, southern Utah, New Mexico, Mexico and 

Chapter HI 109 Angiosperms 

the borders of Lower California, and it is particularly abundant in the Colo- 
rado and Mohave deserts. It flowers from June to September and appears 
to be an important cause of hayfever in southern California and Arizona. 

The shadscale or spiny saltbush (A. confertifolia Wats.) is an erect 
shrub, woody throughout, rigidly branched and spiny, about 2y 2 to 7 feet 
high. It is characteristic of alkaline plains of the western slope of the 
Rocky Mountains and the Great Basin area where it is the most abundant 
species on stony planes and hillsides next to sagebrush, and even more 
tolerant of alkali. It flowers from May to August and is regarded as im- 
portant in hayfever in Arizona. 

Rosaceae (The Family of the Roses, Cherry, Peach and Apple) 

The rose family is one of the largest among the flowering plants, com- 
prising more than 100 genera and 2500 species. They are herbs, shrubs and 
trees with alternate simple or compound, stipulate leaves, their flowers 
nearly always perfect and regular with five parted calyx and five petaled 
corolla, generally numerous stamens and one to many carpels. 

This family contains many of our most valuable fruit trees, as apple, pear, plum, 
cherry and peach, and their humbler relatives the raspberries, blackberries and straw- 
berries, and such ornamental trees as the American and European mountain ashes 
(Sorbus), the many different hawthorns (Cratacgus), cultivated for their showy 
flowers and bright red fruits which mature in late autumn, and many garden shrubs, 
as the bridal wreath, steeple bush and meadow sweet (Spiraea). Apparently all are in- 
sect pollinated though most are somewhat imperfectly adapted to entomophily, produc- 
ing more pollen than is actually carried away by insects. 

The pollen grains (fig. 51 A) when expanded are oblate spheroidal, 25 to 52/4 in 
diameter. Normally the grains are provided with three long tapering furrows which 
function freely in accommodating changes in volume of the grain. The furrows are 
crossed by a delicate smooth membrane provided with a central germ pore, but the 
furrow membrane is easily ruptured and is often destroyed in the preparation of the 
grain for microscopic examination. The exine is always distinctly granular and fre- 
quently the granules are arranged in rows presenting a striate appearance similar to 
that of the grains of some maples. The grains are only meagrely supplied with surface 
oil so that they do not clump much at time of shedding. 

There is no doubt that the pollen of some species possesses allergenic potentialities 
but the entomophilous habits of the flowers narrowly limit its effectiveness. 

Of the whole family it appears that the roses are the most important in 
hayfever. Their true importance, however, has been largely obscured by 
the fact that until quite recently many people jumped to the unwarranted 
conclusion that all early summer hayfever was due to the pollen of roses. 
Then discovering that most of this was due to grasses, they jumped to the 
equally unwarranted conclusion that no hayfever was due to roses. Be- 
tween these all or nothing viewpoints lies the truth that roses can cause 
hayfever but seldom do, so seldom in fact, that a case of simple rose hay- 
fever is almost a medical curiosity. The former widespread belief in roses 
as the chief cause of early summer hayfever appears to have an interesting 
historical significance, being carried over from a time before the agricultural 
grasses and weeds were as abundant as they are now, and when what little 
hayfever there was was more often than not caused by the pollen of roses. 
With the coming of the agricultural grasses and weeds of cultivation, the 

Roger P. Wodehouse 110 Hay fever Plants 

roses still held foremost place in the minds of many who saw only the roses, 
partly because of the inconspicuousness of the real causes and partly be- 
cause of the very convincing evidence of a few hayfever sufferers who 
found that smelling roses would cause them to sneeze. In order to avoid 
this confusion the name "Rose cold" should be reserved for the relatively 
few cases of hayfever which are actually due to the pollen of roses. 

Most roses of modern cultivation are so completely doubled that they 
produce only infinitesimal amounts of pollen. The doubling of a rose entails 
the conversion of the stamens, which normally produce pollen, into petals 
which produce no pollen but enhance the beauty of the flower. It appears 
that the small traces of pollen that such roses produce is sufficient to affect 
hayfever patients who handle them, or even the scent alone, as suggested 
by BIEDERMAN (1937). However, if one wishes to secure rose pollen in 
any considerable quantity it is a hopeless task to get it from the high bred 
roses ; one must turn to the wild or single varieties. Rosa rugosa, a strong 
rapidly growing stock species upon which many fine varieties are cus- 
tomarily grafted, and which is frequently used as a hedge plant without 
grafting, is a prolific pollen shedder. Most single varieties and wild species 
also produce fairly large amounts of pollen. 

Besides the roses several species of Spiraea have occasionally been thought to 
cause hayfever, the common hardhack or steeple bush (S. tomentosa L.), for example, 
and such cultivated forms as the bridal wreath (S. prunifolia S. & Z.) and 6*. Thun- 
bergii Sieb, The cultivated fruit trees such as the apple (Pyrns Malus L.), pear 
(Pyrus comnwnis L.), cherry (Prunus Cerasus L.) and the peach (Prunus Persica 
S. & Z.) have occasionally been thought to cause hayfever. Their pollen appears 
to have the capacity to induce sensitization but the physical characters of both it and 
the flowers are such that it could become an important factor in hayfever only under 
unusually close association with the plants, 

Platanaceae (Sycamore or Plane-Tree Family) 

The Sycamore family comprises only the genus of the plane-trees (Plat- 
anus). These are tall handsome trees with smooth exfoliating bark, alter- 
nate palmately lobed leaves. The leaf petiole is hollow at its base and com- 
pletely encloses the leaf bud of the following year. The flowers are entirely 
wind pollinated. They are inconspicuous and open late in spring with the 
unfolding of the leaves. They shed large amounts of buoyant pollen which 
is freely caught on pollen slides. The pollen grains (fig. 5 IB) when fully 
expanded are oblately flattened, 18 to 2 1//, in diameter, provided with three 
or sometimes, four broad furrows with their membranes copiously flecked 
with granules and without germ pores. The exine is thin and finely reticulate 

The sycamores comprise about 6 species confined to eastern and western 
North America, Central America and southwestern Asia. They are all 
similar and closely related, and some have been shown to be important 
causes of hayfever. The common native sycamore of the East is Platanus 
occidentalis L., also known as plane-tree, button-wood and button-ball. It 
is particularly abundant along streams and in wet woods and is frequently 
cultivated throughout the eastern United States and westward to Minne- 

Chapter III 111 Angiosperms 

sota and Texas. It is one of the largest deciduous trees in the East, reach- 
ing a height of 130 feet with a trunk diameter of 14 feet. Its inconspicuous 
flowers are borne in round heads. Opening in May they shed large amounts 
of pollen which is abundantly caught on pollen slides, and appears to cause 
some hayfever; BROWN (1932) states that it is next in importance to the 
oaks in the Middle Atlantic States. 

In California is found another native species, the western sycamore (P. 
racemosa Nutt.). It is generally a smaller tree than the eastern species, 
scarcely reaching 90 feet in height, and bears its rounded flower heads, both 
staminate and pistillate, in pendent racemes of three or more. It sheds an 
abundance of pollen and appears to cause some hayfever. It is common on 
the banks of streams in western California. 

Besides these two native species, the London plane (P. acerifolia Willd.), 
an exotic species of uncertain origin, is much planted as a street tree in the 
eastern states and in California. This species appears to be sometimes con- 
fused with the western sycamore which it resembles but from which it can 
be distinguished by having its flower heads in twos instead of in racemes of 
three or more. It is also sometimes confused with the oriental plane-tree 
(P. orientalis L.), an Asiatic and European species which is only rarely 
grown in America. The London plane-tree is regarded by HALL (1922)' 
as a cause of hayfever in California. 

Mimosaceae (The Mimosas, Acacias and Mesquites) 

The mimosa family comprises about 40 genera and more than 1500 
species of herbs, shrubs and trees, mostly of tropical distribution. They are 
considered to be closely related to the Fabaccae, and are by many authors 
joined with them, the Caesalpiniaceae and Kramcriaceae, to form the family 
Leguminosae. The flowers are small with generally a minute calyx and 
corolla, and are borne in dense heads or spikes. The stamens are numerous, 
their filaments long, protruding much beyond the corolla and giving the 
flowers the appearance of being anemophilous. There seems to be no doubt, 
however, that they are primarily, if not entirely, entomophilous. Those of 
many species are sweet scented, brilliantly colored and attract insects and, 
what is even more important, most species produce relatively little pollen in 
spite of their numerous stamens. 

The pollen grains of this family exhibit an enormous diversity of form, those of 
some of the different genera having no visible resemblances to each other. This seems 
to be due to the fact that the grains of most species are variously compounded in 
groups of four or multiples of four, the union exerting so strong an influence on 
their form that their basic phylogenetic characters are largely suppressed. The grains 
of the sensitive plant (Mimosa pudica L.) are united in compact tetrahedral tetrads. 
They are extremely small, the whole tetrad measuring only 9 to 9.5/tt in diameter. 
Their exine is thin and exhibits no trace of pores or furrows. The grains of Acacia 
(fig. SID) are further compounded, generally occurring in groups of 16, composed of 
four united tetrads. But the grains of Acacia pollen are considerably larger, the 
individual cells measuring about 17A* in diameter, and the germinal furrows, though 
only vestigial and entirely functionless, conform in their arrangement to the trischisto- 
clasic system as far as its expression is possbile under the limitations imposed by the 
union of the grains. The grains of mesquite (fig. 51C) always occur singly, and they 

Roger P. Wodehouse 


Hayfever Plants 

:onform in every respect to the basic form of the Fabaceae and, in fact, the other 
Mosaics with which this family is associated, characterized by three meridionally ar- 
anged furrows without pores, and with faintly granular exine. There is no doubt 
hat mesquite is closely related to Mimosa and Acacia, yet the form of its pollen grains 
s of the type one would expect to find in association with the Resales instead of being 

FIG. 51. POLLEN GRAINS: A, Rose (Rosa mgosa) ; B, Sycamore (Platanus) ; 
C, Mesquite (Prosopis glandulosa) ; D, Acacia; E, Olive (Olea ciiropaea) ; F, White 
ish (Fraxinus americana) ; G, Norway maple (Acer platanoides) ; H, English plantain 
(Plantayo lanceolata). All magnified 1300 times. 

Chapter III 113 Angiosperms 

like those of Mimosa and Acacia. So it seems logical to deduce that the extreme modi- 
fication of form encountered in the grains of Mimosa and Acacia is the result of their 

Only the acacias, mimosa tree and mesquite of this family have ever been 
suspected of causing hayfever and even they can be of only relatively little 


The acacias comprise about 450 species, not always clearly defined, of 
small trees or shrubs, widely distributed throughout the tropics, especially 
in Australia. Several species are native of America, characteristic of the 
hot and arid regions of the Southwest. One of the best known is the 
opopanax or huisache (A. Farncsiana Willd.), also called popinack and 
cassie. It is a small tree, 20 to 30 feet high, with spreading spiny branches 
bearing bright yellow flowers closely compacted in small globular heads, 
opening in February and March. It occurs naturally from Texas to Chili, 
but is now distributed through introduction almost throughout tropical and 
subtropical regions. Though the flowers present the appearance of being 
wind pollinated they are probably not, for they are so sweetly scented that 
the plant is cultivated in the Mediterranean region for its perfume. 

In the warmer parts of the United States, especially California, several 
species of Acacia are grown for ornament, for example the Sydney golden 
wattles (A. longijolia Willd.) with beautiful yellow flowers in long axillary 
spikes, as much as 2*4 inches long. In hothouses throughout the world 
many other species are grown. 

The status of acacia pollen as a cause of hayfever appears to be not quite 
clear. Of it HALL (1922) says: "Popularly supposed to be a cause of 
spring hayfever, but this is almost impossible except by direct inhalation. 
The pollen is produced very sparingly and is not easily carried by the wind". 
The popular belief in its hayfever producing proclivities, however, is prob- 
ably not entirely unfounded, for ROWE (1928) says, "Acada pollen, though 
usually carried by insects, has been found on our plates, and it causes definite 
hayfever and asthma in some cases". Later ROWE (1931) finds that the 
pollen, though occurring only in small quantities is extremely toxic: "It 
produces not only hayfever and asthma but dermatitis and pollen toxemia". 
Also DEAMER and McMiNN (1935) report Acacia pollen on their pollen 
plates from various parts of San Francisco. These reports, however, are 
still open to question. 

Prosopis (The Mesquites) 

The mesquites are deciduous shrubs or small trees, armed with spines 
or thorns. They resemble the acacias and appear to be very closely related 
to them. Their flowers are like those of acacia but with separate petals and 
only 10 stamens. Two species are common in the arid regions of America. 

The honey mesquite (P. juli flora DC., P. glandulosa Torr.), also called 
honey locust and algaroba, is a low spreading shrub with a large thick tap- 
root which is said to descend to a depth of 40 to 50 feet and with rudimentary 

Roger P. Wodehouse 114 Hayfever Plants 

horizontal roots spreading iix all directions. On account of its extraordinary 
root system the plant is able to survive and maintain a flourishing green 
crown in almost the driest deserts, and is perhaps the most characteristic 
shrub of the arid regions of the Southwest from Louisiana to Arizona and 
Mexico and northward to Kansas. It flowers from May to July, producing 
spikes of minute greenish yellow flowers which are sweet scented and un- 
doubtedly primarily insect pollinated but strongly suggest by their appear- 
ance and the large amount of pollen that they shed that they may also be 
partly wind pollinated. There also seems no doubt that this pollen can pro- 
duce hayfever. Of it SELLERS (1934) says: "In wide areas of west Texas 
the most important tree causing hayfever in the spring is the mesquite. This 
tree begins to pollinate in late April and continues to do so intermittently 
until July. Its pollen is both wind and insect borne". This same author in 
an earlier article (SELLERS 1929) reports 10 cases in Texas having symp- 
toms of hayfever starting in April or early May and continuing at irregular 
intervals throughout the summer, which were definitely proved to be due 
to mesquite and were benefited by treatment with its pollen. In a discussion 
rf this article, DR. I. S. KAHN reports that in Honolulu mesquite is claimed 
to cause a good deal of hayfever. 

The wood of the mesquite has been demonstrated to cause dermatitis 
(Fox 1941). 

The screw-pod mesquite, Mexican screw bean or tornillo (P. pubescent 
Benth., Strombocarpus pub esc ens Gray) is of similar habit and appearance 
but may be distinguished by its tightly curled seed pods. It occurs in sandy 
ind gravelly washes from Texas to southern California, north to Colorado 
md Nevada, and in Mexico. It is common in the Colorado and Mohave 
leserts and even in parts of Death Valley. It flowers from early spring to 
nidsummer and, like honey mesquite, suggests by the appearance of its 
[lowers that it may be partly wind pollinated, but it is not known to cause 

The mimosa tree {Albizzia Julibrissin Durazz.) is a shrub or small 
tree with scaly bark, and leaves twice pinnately divided giving them a fern- 
like appearance. It bears large clusters of pink or whitish flowers during 
spring and most of the summer. It is native of Asia but now widely culti- 
vated and naturalized in the South from Virginia to Florida and Louisiana, 
ft is not known to cause hayfever but has occasionally been suspected of 
doing so. Its common name of mimosa is a survival from a time when it 
md the acacias were included in the genus Mimosa. 

Fabaceae (The Pea Family) 

The pea family comprises about 325 genera and more than 5000 species 
?r herbs, shrubs, vines and trees, with compound leaves and irregularly 
Dapilionaceous flowers. All are entirely insect pollinated and most of them 
remarkable for the perfection of their adaptation to entomophily. They 
>hed only minute quantities of pollen and their stamens are generally con- 
:ealed in the fold of the lower petal in such a way that their anthers can not 
3e exposed except by the action of an appropriate insect releasing the 

Chapter III 115 Angiosperms 

mechanism. It seems unreasonable to look for causes of hayfever among 
plants in which the pollen is so efficiently guarded and dispensed, yet several 
species have been suspected and apparently with some justification. 

One of those most frequently blamed for hayfever is alfalfa (Medicago 
sativa L.). It is a much branched spreading herb resembling clover, with 
deep violet or blue flowers during most of summer. It is native of Europe 
but much cultivated for fodder and hay almost throughout the United 
States. The stamens are held at maturity under tension but So arranged 
that they may be tripped by a visiting insect when the anthers strike him 
on the thorax (BRINK and COOPER 1936). It would thus appear unlikely 
that under normal conditions enough pollen could ever become scattered 
in the air to become atmospheric. Still FOSKETT ( 1929) reports two hay- 
fever cases found to be sensitive to alfalfa pollen. They lived with alfalfa 
plants growing right up to their door. Upon being treated with an extract 
of alfalfa pollen they were relieved of their hayfever. ELLIS and ROSENDAHL 
(1933) point out that alfalfa and clover are cut and cured at their time of 
bloom and much shattering of flowers undoubtedly occurs offering the 
possibility of hayfever from the curing of alfalfa hay. 

Several clovers (Trijolium} have attracted attention as possible causes of hayfever 
but probably with still less justification. One of the commonest is the beautiful red or 
purple clover (T. pratensc L.), a European species which may be found flowering 
from early spring to late fall in moist fields and meadows throughout most of the 
United States. Often associated with it is the pink or alsikc clover (T. hybridum L.) 
and the white, Dutch or honeysuckle clover (T. re pens L.). 

White and Yellow sweet clovers (Melilotus alba Desv. and M. offidnalis Lam.) 
are naturalized and widespread weeds, flowering throughout the summer. It is prob- 
ably only on account of their abundance and close association with human habitations 
that they have been accorded a place in hayfever literature. 

Among the arborescent forms of the Fabaceae the locust (Robinia pseudoacada L.) 
is sometimes given consideration in hayfever studies but, like the other members of 
the family, it could only cause hayfever under most unusual circumstances. 

The pollen grains of the pea family are somewhat various. They are prevailingly 
three furrowed and their exines are striate or finely reticulate. The grains of alfalfa 
and sweet clover can easily be distinguished by their size and the markings of their 
exines (WODEHOUSE 19426, PI. VIII, 79, 80). JAMIESON (1939) states that the grains 
of Trifolium hybridum can be distinguished from those of T. repens and from those 
of alfalfa by the degree of coarseness of the reticulum of their exines. 

Simarubaceae (Ailanthus or Quassia Family) 

The ailanthus family comprises about 150 species in 30 genera of trees 
and shrubs mostly native of warm or tropical regions. Its only interest 
from the hayfever standpoint is through the tree-of -heaven {Ailanthus al- 
tissima Swingle). This is a small to medium-sized tree much planted for 
its attractive and exotic appearance which it owes partly to its long pinnate 
leaves, 1 to 3 feet long, with 13 to 41 leaflets, and partly to its large panicles 
of ill scented greenish-white flowers which are produced in June. They are 
primarily insect pollinated, but they are obviously only poorly adapted to 
entomophily, for much pollen is liberated to be blown away by the wind, 
and is readily caught on atmospheric pollen slides during most of June. 

Roger P. Wodehouse 116 Hay fever Plants 

Its pollen grains (fig. 58A) when moist are oblately flattened, about 26^ 
in diameter, provided with three long tapering germinal furrows with 
smooth membranes and each with a clearly defined germ pore. The exine 
is rather thick and coarsely reticulate with the reticulations tending to be 
linearly arranged. 

The tree is native of China but escaped from cultivation and thoroughly 
naturalized practically throughout the United States, and in many places is 
regarded as a pest. It is said to cause hayfever in China and has recently 
been reported as doing so in the United States (BLUMSTEIN 1943). 

Tiliaceae (Linden Family) 

The linden family comprises a large number of trees and shrubs of 
world-wide distribution. But they are represented in the United States by 
only three genera, Corchorus and Triumjetta of extreme southern regions, 
and Tilia of more northern distribution. Only the latter has ever been 
given serious consideration as a cause of hayfever. 

Tilia (Linden, Basswood) 

The basswoods are fine trees with soft white wood, broad heart-shaped 
leaves and showy white or cream-colored flowers borne in clusters sub- 
tended by a large leaf-like bract. The flowers are peculiarly fragrant and 
notable for the large amounts of honey obtainable from them. Though en- 
tirely insect pollinated they are copious pollen shedders and their pollen 
can easily be demonstrated in the air at considerable distances from the 
flowering trees. That it could occasionally cause hayfever is to be expected. 
Indeed DERBES (1941) has reported such cases. 

Several species occur naturally in the United States. The most abundant 
is T. ainericana L., Basswood or Whitewood, widely distributed throughout 
the eastern half of the United States. The European linden (T. europaca 
L.) is most frequently cultivated in and near cities as a shade tree. It 
occurs in several varieties which are selected by horticulturists for various 

The different species and varieties of linden may flower at widely different times 
so that their flowering period extends over several months, from May to July. 

Linden pollen grains are uniform in size, lens shaped, about 36.5ju in diameter and 
28/u, thick. They are provided with three, or occasionally four, germ pores deeply 
sunken in their short pit-like furrows. The exine is rather thick and finely reticulate. 
There is no other atmospheric pollen grain which those of Tilia even remotely re- 

Aceraceae (The Maple Family) 

The maple family comprises only the maples and the single Asiatic species, 
Diptcronia sincnsis Oliv., which is native of central China but occasionally 
cultivated as an ornamental in the warmer parts of the United States. 

Acer (The Maples) 

The maples are trees or shrubs with watery sap which is often sugary, 
comprising about 115 species of wide distribution over most of the northern 

Chapter III 117 Angiosperms 

hemisphere and, in one species, extending south of the equator in the moun- 
tains of Java. The leaves and twigs are opposite or occasionally in whorls 
of three. The leaves are long petioled, simple, palmately 3 to 7 lobed or 
nerved, or in one species 3 to 7 foliate. Some species are entirely en- 
tomophilous and one (A. N eg undo) entirely anemophilous, but most appear 
to be amphiphilous, exhibiting various degrees of adaptation to pollination 
by both insects and wind. The flowers are regular but only occasionally all 
perfect. There appears to be a rough correlation between the completeness 
of the separation of the sexes and the degree of adaptation of the flowers to 
wind pollination. 

The pollen grains of the maples (fig. 51G) are rounded triangular or 
spheroidal and oblately flattened when fully expanded. They have usually 
three furrows which are long and tapering to pointed ends, almost meeting 
at the poles, their membranes smooth and without germ pores. Usually 
there are some grains with supernumerary furrows which may or may not 
conform to the trischistoclasic system. The exine is finely reticulate pitted 
or granular, the one condition sometimes shading into the other on the 
same grain. The granules or pits may or may not be linearly arranged in 
striae which assume the form of thumb-print markings. In the grains of 
A. platanoides the exine is rather thick and definitely and constantly striate. 
In those of A. Pscudoplatanus the exine is thinner but still striate. In those 
of A. rubrum the exine is fully as thick and even more markedly striate than 
in the grains of A. platanoides. But in those of A. saccharinum and A. 
saccharmn the exine is thinner and not consistently striate, the majority 
of the grains showing no trace of striae, and in those of A. Negundo the 
exine is very thin and entirely without striae. The grains with the thickest 
and most definitely striate exines are found among those whose flowers are 
mostly or entirely insect pollinated and those with the thinnest and least 
striate exines are found among those whose flowers are nearly or entirely 
wind pollinated. 

Entomophilous Species : Among those which appear to be entirely 
entomophilous are the Norway maple (A. platanoides L.). It is native of 
Europe but throughout most of the United States is a favorite tree for street 
planting and as an ornamental in parks and gardens. It occurs in many 
forms which are much prized in cultivation for the color of their leaves 
and the way in which they are cut. The flowers, which open in May at 
about the same time as the leaves, present the appearance of being com- 
pletely entomophilous. They are about l /$ inch in diameter, provided with 
calyx and corolla, greenish yellow in erect or nodding many flowered, stalked 
corymbs. There is only a slight tendency toward the separation of the 
sexes, both perfect and unisexual flowers occurring on the same or dif- 
ferent trees, a condition spoken of as andropolygamous. 

Similar in these respects is the sycamore maple (A. Pscudoplatanus 
L.). Its flowers are also andropolygamous, greenish yellow and with both 
calyx and corolla, but somewhat smaller, and are borne in pendulous racemes, 
2 l /2 to 5 inches long, appearing late in May after the leaves have almost 

Roger P. Wodehouse 


Hayfever Plants 

fully developed. It is a medium-sized round-topped tree, native of Europe 
and Asia where it has been cultivated for centuries. In the United States 
it is a favorite for street and park planting. While both of these trees are 
probably entirely insect pollinated, their adaptation to this mode of polli- 
nation is obviously imperfect, and some pollen is scattered and may appear 
in the air in sufficient quantity to become at times a factor in hayfever. 

Amphiphilous Maples : Among those which appear to be partly 
pollinated by insects and partly by wind are such familiar trees as the red 
maple, silver maple and sugar maple. These have flowers which are attrac- 
tive to insects, but their stamens are exserted and shed more pollen than is 
carried off by insects, and it can easily be detected in the air. Of these the 

FIG. 52. Red maple (Acer rubrum), flowering twig and enlarged flower. 

red maple (A. rubrum L., fig. 52) also called scarlet, white, swamp or soft 
maple, is a handsome tree from 80 to 120 feet high. It is one of the com- 
monest and most generally distributed in North America. It occurs prin- 
cipally in rich moist soil, taking readily to swamps, throughout the eastern 
states and westward to Manitoba and Texas. It flowers from March to 
April, its bright scarlet or yellowish flowers appearing long before the 
leaves. The flowers are small, the staminate and pistillate aggregated in 
different fascicles on the same or different trees. Each flower is provided 

Chapter III 



with a small calyx and corolla beyond which the stamens protrude. They 
are sweet scented and eagerly sought by bees. Nevertheless the pollen is 
scattered in the air and may at times become a menace to hayfever sufferers. 
The silver maple (A. saccharinum L.) also called white, river, soft or 
swamp maple, is similar in appearance and habit to the red maple, but it 
flowers earlier, generally in February and March, depending upon the lo- 
cality and season, and its flowers are yellowish green. They are sessile or 
short stalked and closely aggregated in fascicles. The calyx is minute and 
five lobed, as in A. rubrum, but the corolla is entirely absent. The stamens 
are prominently exserted and the staminate and pistillate flowers in different 
clusters on the same or different trees. The silver maple is a tall handsome 
tree, 90 to 100 feet high, abundant throughout the eastern states and as far 
west as the Dakotas and Oklahoma. It occurs in several varieties which 
are favorites for street planting. It is also sometimes used as a source of 

FIG. 53. Sugar maple (Acer saccharum}, flowering twig. 

sugar but said to be less satisfactory than sugar maple. It appears to be 
primarily insect pollinated but less so than its close relative the red maple. 

The sugar maple (A. saccharum Marsh., fig. S3) also called rock, 
hard, black or sweet maple is both wind and insect pollinated. The flowers 
open at the same time as the leaves in April or May. They are borne on 
long drooping pedicels in nearly sessile umbel like corymbs. Each little 
flower is provided with a five lobed calyx greenish yellow in color, but with 
no corolla. The staminate and pistillate flowers are in the same or separate 
clusters on the same or different trees. The stamens have unusually large 
anthers which protrude from the calyx suggesting a strong tendency toward 
anemophily. They are, however, freely visited by bees so they are at least 
partly entomophilous. 

The trees are large and stately components of our deciduous forests 
from Newfoundland to Florida and westward to Texas. There occur 

loger P. Wodehouse 


Hayfever Plants 

everal varieties which are much prized for street and park planting. This 
pecies is the source of most of the maple sugar. 

Anemophilous Species: The boxelder (A. Ncgundo L., Negundo 
ceroides Moench, Rulac Negundo Hitchc., fig. 54) also known as ash- 
iaved or cutleaved maple, or water ash, is undoubtedly entirely wind polli- 
ated. Its flowers, which expand just before the leaves, in April, are yel- 
)wish green borne on long slender drooping pedicels, the staminate in 
iscicles, the pistillate in narrow drooping racemes, those of the two sexes 
n different trees. Each little flower is provided with a minute five-lobed 

FIG. 54. Boxelder (Acer Negundo}, flowering twig. 

alyx and 4 to 6 stamens but no corolla and the stamens with their large 
nthers hang out beyond the calyx and appear to shed much more pollen 
lan those of any other maple. 

Boxelder is a small to medium-sized tree, seldom reaching over 70 feet, 
enerally wide spreading with the trunk dividing near the ground. Its 
lost distinctive character is that of its leaves which are usually divided into 
iree, occasionally five to seven, leaflets. It is found growing naturally 
long the banks of streams and lakes and the borders of swamps throughout 
astern North America as far west as Nebraska and Texas, and is exten- 

Chapter III 121 Angiosperms 

sively planted as a street tree in the cities of Utah and used as a windbreak 
in the Missouri valley states. Near the Atlantic coast it is frequently 
planted along streets and in parks but is otherwise scarce. It also occurs in 
the Rocky Mountain region from Saskatchewan to Mexico, and in Cali- 
fornia. The trees of these regions are slightly different and are designated 
respectively as var. interior Sarg. and var. californica Sarg. 

Oleaceae (Olive Family) 

The olive family comprises about 400 species in 20 genera of trees and 
shrubs. Most are entirely insect pollinated and of little interest in hayfever 
studies. Some are cultivated for the beauty and fragrance of their flowers. 
Among such are the lilac (Syringa), an Asiatic genus of which some five 
or six species and many varieties are cultivated in America, and the jasmins 
(Jasminum), a huge genus of tropical climbing or erect shrubs of which 
about fifteen species are cultivated particularly in the southern states, and 
goldenbells (Forsythia), well known to all as the first flowers of the garden 
to appear in spring. These are all closely insect pollinated and could hardly 
be considered as hayfever plants though they have occasionally been sus- 
pected. On the other hand the olive and privets, though obviously en- 
tomophilous, are only imperfectly adapted to this mode of pollination so 
that much pollen escapes into the air. The ashes are some insect and some 
wind pollinated and are of real importance in hayfever. 

The pollen grains of the Oleaceae considered here are spheroidal or 
oblately flattened and with three meridionally arranged furrows (occa- 
sionally four or more) without well defined pores. The exine is variously 
but always conspicuously reticulate (WODEHOUSE 1935). 

Olive (Olca europaea L.) is a small spreading tree about 25 feet high with tough 
evergreen leaves dark above but silvery and scurfy below, arranged oppositely on the 
branches. The flowers appearing in April and May are small and white, dioecious or 
polygamous, somewhat resembling those of privet but sweet scented. They are un- 
doubtedly primarily insect pollinated but appear to be also partly wind pollinated for 
they scatter large amounts of pollen which is known to cause some hayfever in parts 
of California and Arizona where the trees are extensively grown for their fruit 
(PHILLIPS 1932). 

Their pollen grains (fig. 51 E) are about 22# in diameter, with generally three or 
occasionally four furrows which have jagged margins and flecked membranes. The 
mesh of the reticulum is rather coarse, coarser than that of the grains of Fraximts but 
less so than in those of Ligustrum. 

Ligustrum (The Privets) 

The privets are deciduous or evergreen shrubs with opposite leaves, 
bearing numerous small white flowers in compact terminal panicles, re- 
sembling those of lilac but less showy, and disagreeably scented. Their 
flowers are undoubtedly primarily insect pollinated but their adaptation to 
this mode of pollination is so loose that they may even be partly wind polli- 
nated ; if a flowering privet bush is shaken on a still day quantities of pollen 
can be seen to float away in the air. Privet pollen is frequently caught on 
atmospheric pollen slides and has been shown to be an important cause of 

fcoger P. Wodehouse 


Hayfever Plants 

layfever in regions where the bushes are abundant and allowed to flower. 


The pollen grains are similar to those of olive but with thicker and 
nore closely reticulate exine and with their furrows more sharply defined. 

The genus comprises about 50 species, native of Asia, Australia, and one in the 
Mediterranean region. About a dozen are cultivated in America, planted for their 
rnamental foliages or their flowers which open mostly in late spring or early summer, 

FIG. 55. Privet (Ligustrum oi'alifolium) , flowering twig and enlarged flower. 

>r for hedges in which case they are generally prevented from flowering by frequent 

The California privet (L. ovalijoUum Hassk., fig. 55) is the one most usually cul- 
ivated in the North. When used as a flowering shrub it may reach a height of 15 feet 
>r more, bearing numerous panicles of white flowers in June and July. The flowers 
ire tubular like those of lilac, each with two stamens with their anthers projecting 
>eyond the corolla so that if the pollen is not carried away by insects it is easily scat- 

Chapter III 123 Angiosperms 

tered. The common privet (L. vulgar e L.) is similar but may be distinguished by its 
shorter corolla tube with the stamens included; also it is entirely deciduous while the 
California privet is partly evergreen. Both species occur in several varieties, some 
with leaves yellow or variegated with white, which are used as ornamentals and for 

The ibota privet (L. Ibota Sieb.) is also frequently cultivated. It is a smaller and 
more graceful shrub with pubescent branches and leaves pubescent on the under side; 
it is an attractive garden shrub and has an advantage in not shedding nearly so much 
pollen as common or California privet. 

The southern or glossy privet (L. lucidum Ait.) is the species most frequently 
planted in the South. It is a shrub or small tree with thick leathery evergreen leaves 
and small white flowers opening in spring. It appears to have hayfever possibilities 
similar to the California privet. 

In hayfever studies the species of privet are rarely distinguished from 
each other so it is not known if there are allergenic distinctions between 
their pollen. 

Fraxinus (Ash) 

The ashes comprise about 65 species of deciduous trees mostly of the 
north temperate zone, with opposite usually pinnate leaves and opposite 
branches. Their flowers are various, depending upon their mode of polli- 
nation. Of those which are insect pollinated the flowers are perfect with 
corolla, and fragrant, somewhat resembling those of privet and olive, and 
appearing in spring with or after the new leaves. Such a tree is the flower- 
ing ash (F. Ornus L.), a handsome tree bearing fragrant white flowers in 
May and June, native of southern Europe and western Asia, but frequently 
cultivated in the warmer parts of the United States. A similar species is 
the native F. cuspidata Torr., a shrub or small tree of western Texas and 
New Mexico, with fragrant white flowers appearing in April. It is regarded 
as a possible cause of hayfever (WATRY and LAMSON 1934). There are 
also several Asiatic species occasionally cultivated in America which, like 
F. Ornus and F. cuspidata, are insect pollinated. But the majority of 
ashes in America are entirely wind pollinated and notorious for the large 
amounts of pollen which they shed. These have unattractive flowers without 
corollas and even sometimes without calyces. Many of them are handsome 
trees, frequently used in street and park plantings. And they constitute a 
real menace to hayfever sufferers, sometimes counted among the most im- 
portant hayfever trees. 

The pollen grains (fig. 5 IF) of F. americana and F. velutina are 20 to 
25/x in diameter, flattened and angular in outline with generally four, less 
often three or five, furrows, one at each angle, their membranes flecked and 
margins jagged. The exine is thin with its reticulum less strongly devel- 
oped than in the grains of other members of the family and ending along the 
furrows with open lacunae. 

White ash (F. americana L.) is a tall forest tree reaching over a hundred 
feet in height, with dioecious flowers opening in spring just before the 
leaves, and shedding huge quantities of buoyant pollen. It occurs in moist 
rich soil almost throughout the United States east of the Rocky Mountains, 
reaching its best development in the bottom lands of the basin of the lower 

Roger P. Wodehouse 124 Hay fever Plants 

Mississippi River; northward and westward of the Mississippi River it is 
less common and of smaller size. 

Red ash (F. pennsyhanica Marsh.) is a similar tree but smaller, 40 to 
60 feet high, flowering late in spring just as the leaves begin to unfold, and 
with similar distribution, reaching from Nova Scotia to Manitoba and 
southward to southern Georgia, Alabama and Mississippi. The species is 
very variable and several varieties have been recognized. Perhaps even 
better known than the species itself is the green ash (F. pennsyhanica 
lanceolata Sarg.). By some this is regarded as a distinct species and known 
as F. lanceolata Borkh. or F. viridis Michx. f. It is a small tree seldom 
more than 60 feet high with ashy gray branchlets marked by pale lenticels. 
It has a more southerly distribution, from Maine to Florida and westward to 
Saskatchewan, Montana and Texas, most abundant in the basin of the 
Mississippi River and eastern Texas, and appears to be the most important 
ash of the South. It is one of the seven species of trees found capable of 
surviving the rigorous climate of the shelter belt at Mandan, North Dakota, 
showing there a resistance second only to that of the Chinese elm (GEORGE 

Mountain ash (F. Sarg.) is a small tree, rarely reaching 50 feet 
in height, with stout dark green branches tinged with red, and downy when 
young, flowering in March as the leaves begin to unfold. It is found on the 
high dry limestone bluffs and ridges in the neighborhood of Dallas and Fort 
Worth, the valley of the Colorado River near Austin and similar places in 
Texas. The term, 'mountain ash' is more commonly used to designate 
Sorbus amcricana Marsh, and S. Aucuparia L., the latter more properly 
called the European mountain ash or rowan tree, both insect pollinated 
members of the rose family and of no importance in hayfever. 

Arizona ash (F. velutina Torr.) is a small tree scarcely over 30 feet in 
height, with velvety pubescent branchlets and leaves with three to five 
leaflets pubescent below. It is common in mountain canyons, along desert 
streams and borders of lakes or springs in southern Arizona, New Mexico 
and eastern Texas. It flowers in March or April with the unfolding of the 
leaves. Several varieties are recognized; the desert or leatherleaf ash (F. 
velutina coriacea Rehd., F. coriacea Wats.) distinguished principally by its 
thicker and leathery leaves and less pubescent branchlets. It has a wider 
distribution reaching from southern Utah to southern California, and is fre- 
quently cultivated. A still more glabrous form (var. glabra Rehd.) is cul- 
tivated in the cities of Arizona. F. velutina Toumeyi Rehd. is a form with 
5 to 7 lanceolate or elliptic leaflets smooth on the upper surface but pubescent 
below. It is sometimes regarded as a separate species (F. Toumeyi Britt, 
F. attenuata Jones), and is the form generally known as Arizona ash since it 
is commoner in Arizona than the others, and it is the one generally planted 
as a shade tree in the streets of towns in southern Arizona. It is, however, 
less common in New Mexico. 

Oregon ash (F. oregona Nutt.) is a fairly large tree reaching 80 feet in 
height with a narrow upright head or broad shapely crown, usually in rich 
moist soil in the neighborhood of streams in the coastal region from British 

Chapter III 125 Angiosperms 

Columbia to the San Francisco Bay region of California, and in the western 
foothills of the mountains of San Bernardino and San Diego Counties. It 
flowers in April and May with the unfolding of the leaves, and is regarded 
as one of the most important causes of hayfever in early spring in Oregon 

Plantaginaceae (The Plantain Family) 

The plantain family comprises three genera and about 225 species but 
only those of the following genus are of interest in hayfever studies. 

Plantago (The Plantains) 

The plantains are low herbs, mostly stemless, the scapes arising from 
a rosette of basal leaves and bearing terminal spikes or heads of small in- 
conspicuous greenish or brownish flowers. Calyx and corolla are both 
present, generally four parted, minute and inconspicuous. One species, P. 
Psylliuin, native of India furnishes the valuable psyllium seed. A case of 
allergy to this has recently been reported (AsciiER 1941). The patient was 
a pharmaceutical worker, affected by the ground seeds with which he 

The pollen grains (fig. 51H) are spheroidal, 16 to 40/* in diameter, with- 
out furrows but provided with 4 to 14 pores which are circular or irregular 
in outline and variously scattered, their membranes flecked or provided with 
a single central thickening. The exine is always thin and more or less rough 
granular or mottled. In these characters there is considerable variation 
among the different species so that the grains of the common species can 
generally be easily told apart. 

The genus comprises about 200 species of wide distribution. Of these 
about 20 are native or naturalized in North America. Apparently all are 
entirely wind pollinated but only the English plantain (P. lanceolata L., 
fig. 56) sheds enough pollen and is itself abundant enough to cause hay- 
fever. It is a low herbaceous weed producing a basal rosette of prominently 
ribbed leaves from which arise the straight or nodding flowering scapes 
bearing at their summits short dense spikes of flowers. The flowers are 
perfect, first functioning as female then as male ; as anthesis progresses from 
the base to the tip of the spike, the upper flowers of the spike, while still 
unopened, may be seen to protrude their single unbranched filiform styles 
exposing their longitudinally stigmatic surface to receive pollen, while the 
flowers below are seen to have opened and lost their styles, instead having 
four stamens, their anthers protruding far out on slender filaments and 
scattering their pollen which is blown freely away by the wind. 

English plantain begins to flower in April or early in May and continues 
throughout the summer, but the bulk of its flowering takes place in May 
and June, a period almost coinciding with the worst of the grass hayfever 
season. It is native of Europe and Asia but naturalized in fields and waste 
places almost throughout North America, and is undoubtedly an important 
cause of hayfever, though in no way comparable in this respect with the 

Roger P. Wodehouse 


Hayfever Plants 

grasses with which it is generally associated. BERNTON (1925) states that 
4.3 per cent of a series of hayfever cases in the District of Columbia reacted 
to its pollen, and BLUMSTEIN and TUFT (1937) report that 17.5 per cent of 
the early summer hayfever cases in the Philadelphia area were sensitive to 
plantain pollen. 

FIG. 56. English plantain (Plantago lanceolata), plant in flower. 

The pollen grains of the English plantain are enormously various in size, 
ranging from about 25 to 40/u, in diameter. They may always be distin- 
guished from those of the common plantain by their germ pores which are 7 
to 14 in number, almost circular in outline, encircled by a thickened rim and 

Chapter III 127 Angiosperms 

with their membranes provided with a single central thickening, each pore 
thus resembling the single pore of the grains of the grasses. 

Of the other species growing in America the two which are most commonly dis- 
tributed are Rugel's plantain (P. Ruyelii Dene.) and the common or greater plantain 
(P. major L.). Rugel's plantain is probably native of America while the common 
plantain is probably introduced from Europe. Now, however, both are practically uni- 
versally distributed in fields and waste places throughout most of the world. The two 
species are very much alike and obviously closely related. Both have long-petioled 
coarse ovate leaves forming a basal rosette and long cylindric spikes of inconspicuous 
greenish flowers. But they may be distinguished from each other by certain technical 
details of their seed capsules, also by the fact that the leaves of Rugel's plantain are 
generally shining above while those of common plantain are generally dull, and the 
flowering spikes of Rugel's are generally much less dense than those of the common 
plantain. Both species flower almost throughout the summer but they shed so little 
pollen that, no matter how abundant the plants may be, it can never be considered a 
factor in hayfever. BLUMSTEIN and TUFT (1937), however, have shown that the pollen 
of common plantain contains the same antigenic factor as that of English plantain. 

The pollen grains of both Rugel's and common plantain are occasionally caught 
on pollen slides but are easily distinguished from those of English plantain, and perhaps 
more readily from each other than are the plants themselves. Those of Rugel's plantain 
are 22 to 24p in diameter with 6 to 10 germ pores of irregular shape and size not sur- 
rounded by a thickened rim and with their membranes flecked with several small gran- 
ules. The exine is thick and generally more coarsely granular than that of the grains 
of English plantain, or even mottled. The grains of common plantain are smaller, 16 
to 21/4 in diameter, with only 4 to 6 germ pores. These, as in the grains of Rugel's 
plantain, are irregular in size and shape, without thickened rim and with their mem- 
branes flecked with several small granules, but their exine is even more coarsely 
granular and mottled. 

The other species of plantain found in America are generally not weeds of waste 
places and are rarely abundant enough to deserve consideration as possible causes of 

Compos itae (The Composite or Sunflower Family) 

The composite family is distinguished from all others by having the 
flowers, generally more than one, assembled on a common receptacle and 
surrounded by one or more rows of involucral bracts (fig. 57). The result 
of this arrangement is that the heads of flowers present the appearance of 
being individual flowers. Indeed, by early botanists they were so regarded, 
and this conception still survives to a certain extent in the terminology used 
with these flowers. Botanists of today are careful to explain to the un- 
initiated that a daisy, a sunflower or a chrysanthemum is not really a flower 
but an assemblage of a large number of little flowers on the expanded end of 
a flower stalk, and that the white or colored structures which, if the varieties 
are single, radiate from the margin like petals, are not petals, but each a 
specially modified little flower with a strap-shaped corolla. Still the stalk 
which supports the assemblage of flowers is called the peduncle and its ex- 
panded end which bears the little flowers, the receptacle, the same terms 
which are applied to the stalk and its expanded end which bears the parts 
of the flower in speaking of single flowers of other families. And the in- 
florescence of the Compositae is spoken of as being paniculate, corymbose, 
cymose, etc. whereas by definition in the Compositae it is really always 
capitate ; the terms which in other families are used to describe the arrange- 

Roger P. Wodehouse 


Hayfever Plants 

ments of flowers on their stalks are here used to describe the arrangements 
of heads of flowers. In studying the Compositae, therefore, one must often 
speak of the flower heads as though they were individual flowers while 
bearing in mind that they are assemblages of little flowers. But one must 
not speak of the ray flowers as petals nor of the involucral bracts as sepals, 
for this does not have the sanction of botanical usage. 

Not only does the composite flower head look like a single flower but in 
some ways it functions as such. The ray flowers which in many cases look 

FIG. 57. Composite flowers: A, Two flower heads; B, Section of flower head, 
diagrammatic ; C, Disk flower ; D, Ray flower. 

very much like petals often have no other function than attractiveness, 
being quite sterile and producing neither seeds nor pollen. Among the wind 
pollinated members of the family these are always absent, and among the 
ragweeds which are monoecious, the pistillate heads are one flowered and 
the involucral bracts fused, enveloping the single flower as a calyx tube of 
individual flowers often does in other plant families. 

"The Compositae are at once the largest, the most distinct, and the most 
uniform, and therefore the most natural of all orders of Phenogamous 
[flowering] plants". With these words GEORGE BENTHAM (1873) opens 

Chapter III 



his memorable essay, Notes on the Classification, History and Geographical 
Distribution of the Compositac. BENTHAM also says, "I cannot recall a 

(Ailanthus} ; B, Dandelion (Taraxacum} ; C, Short ragweed (Ambrosia elatior) ; D, 
Prairie ragweed (Cyclachacna xanthifolia) ; E, Cocklebur (Xanthium speciosum) ; F, 
Sunflower (Helianthus} ; G, Goldenrod (Solidago} ; H, Sagebrush (Artemisia triden- 
tata) ; I, Chrysanthemum. AH magnified 1300 times. 

single ambiguous species as to which there can be any hesitation in pro- 
nouncing whether it does or does not belong to the order". When this was 

Roger P. Wodehouse 130 Hayfever Plants 

written about 10,000 species were known. Though this number has since 
risen to over 30,000 (SMALL 1917-1919), these words are no less true today_ 
than they were 71 years ago. The family, though the largest of the flowering 
plants, is compact and stands apart without known connections with any 
other group. 

Pollen Grains: The pollen grains of the Compositae are extremely 
various (fig. 58). Nevertheless, all the different forms are the result of 
modifications of a certain basic form which, with little variation, charac- 
terizes by far the majority of the species. This basic form may be described 
as of medium size, spheroidal or slightly oblate when expanded, ellipsoidal 
when dry, with a thick granular exine with conical spines, thin intine, and 
provided with three meridionally arranged furrows which permit the emer- 
gence of the pollen tube or tubes at time of germination, and permit, by 
opening and closing, considerable expansion and contraction of the grain 
without rupturing its walls. Unmodified this form is found in the grains 
of the sunflower (fig. 58F). In these the exine is finely and faintly granular, 
more so at the bases of the spines. The latter are long and sharp pointed 
and can be seen to consist of two parts, a swollen granular base from which 
arises a slender homogeneous shaft tapering to a fine sharp point. The 
three furrows are only moderately long and when the grain is expanded 
each is seen to be crossed by a delicate elastic membrane which bears at its 
center a clearly defined germ pore, through which the germinal papilla, the 
pollen tube Anlage, may bulge more or less prominently. When the grain 
dries and assumes its elongate form the furrows close up tightly, becoming 
converted to shallow longitudinal grooves. 

The grains of the majority of Compositae have well developed spines, 
though their size and shape vary from tribe to tribe. But in the anemoph- 
ilous species the spines are greatly reduced (e.g., the ragweeds and 
cockleburs) or entirely absent (e.g., some mugworts and sagebrushes). 
Another modification is for the exine to be thrown into an elaborate system 
of anastomosing ridges, bearing spines on their crests (e.g., the chicory and 
ironweed tribes), or without spines (e.g., Barnadesia). The furrows also 
vary greatly in length; in some they are very long, almost reaching the 
poles (e.g., prairie ragweed) or they may be reduced to minute pits almost 
coinciding in extent with their enclosed germ pores (e.g., ragweed and 
marshelder). In spite of their wide variation, however, the grains of the 
Compositae are always quite characteristic and easily recognized when en- 

Classification: The huge number of species included in the Com- 
positae have been variously arranged by different authors, but as treated 
today they are generally grouped into 14 tribes. The interrelationships of 
the tribes, as suggested by their arrangement below, are those of BESSEY 
(1915) modified by SMALL (1917-1919). BESSEY gave each of the tribes 
the rank of family, a procedure which as far as I know has not been followed 
by any later investigator. It should be noticed, however, that some botanists 

Chapter III 131 Angiosperms 

treat some of the tribes as separate families while leaving others. For 
example BRITTON and BROWN (1913), JOHN K. SMALL (1923) and PAYER 
(1860) regard the chicory and ambrosia tribes as separate families, desig- 
nating them as Cichoriaceae and Ambrosiaceae, "A curious atavistic return 
to the early 18th century" (SMALL, I.e.). It is true that the chicory tribe 
is the most distinct and easily recognized of the 14 tribes, but the distinctions 
are scarcely important enough by ordinary botanical standards to warrant 
the separation of the group from the family. Its degree of distinctness is 
quite fairly expressed in GRAY'S Manual by giving it what amounts to the 
status of a sub-family (Series Liguh florae). On the other hand the eleva- 
tion of the ragweed tribe to the rank of family is entirely without foundation. 
The authors who do this, as far as I am aware, give no reasons for it. But 
it appears to be the result of attaching far too much phylogenetic significance 
to the modifications which the floral structures of these plants have suffered 
in response to wind pollination. The phylogenetic relationship of the rag- 
weed tribe is most fairly expressed by BENTHAM (1873) and BENTHAM 
and HOOKER (1873) who saw these modifications in their proper per- 
spective, by treating the group as merely a subtribe of the sunflower tribe. 
The closeness in relationship of the members of the ragweed tribe to those of 
the sunflower tribe is of particular interest to allergists who find that rag- 
weed hayfever patients are invariably as sensitive to sunflower pollen as to 
that of ragweed, though resistant to the pollen of Compositae of other tribes. 

Helianthcae, Sunflower tribe 
Ambrosieac, Ragweed tribe 
Helenieae, Sneezeweed tribe 
Arctotidae, African daisy tribe 
Calenduleae, Calendula tribe 
Inuleae, Inula tribe 
Astereae, Aster tribe 
Vernonieae, Ironweed tribe 
Eupatorieae, Boneset tribe 
Anthemideae, Chamomile tribe 
Senecioneae, Groundsel tribe 
Cynareae, Thistle tribe 
Mutisieae, Mutisia tribe 
Cichorieae, Chicory tribe 

Heliantheae : The sunflower tribe is in many ways the most typical 
of the family and is probably the most primitive. The group is best known 
to us through such late flowers of the garden as the sunflower, dahlia, zinnia 
and cosmos, and the black-eyed-susan of the summer meadows. Their 
flower heads generally comprise two types of florets, the small pollen bear- 
ing flowers of the disk, and the large showy radiate flowers of the margin 
which look like petals. The flowers are nearly always obviously insect polli- 
nated, though often somewhat imperfectly, so that some pollen is scattered. 
Owing to this latter fact and their close relationship to the ragweeds, mem- 
bers of this tribe should be regarded as potential hayfever plants, though 
restricted by the lack of buoyancy of their pollen. Sunflower, dahlia, cosmos, 
black-eyed-susan and others, both wild and cultivated, are known to cause 

Roger P. Wodehouse 132 Hay fever Plants 

hayfever when handled by susceptible individuals, and occasionally their 
pollen may even become atmospheric to a small extent. In this respect the 
common sunflower (Helianthus annuus L.) is the most important. In its 
large headed form it is cultivated almost throughout the United States. In 
its small headed form, regarded by some as a separate species. (H. Icnticu- 
laris Dougl.), it grows wild, sometimes in enormous quantity on prairies 
and alluvial ground almost throughout the United States west of the Mis- 
sissippi River. Both forms are undoubtedly contributors to late summer 
hayfever. In the same category is the feverfew (Parthenium Hysterophorus 
L.). It is one of the commonest weeds of vacant lots throughout much of 
the South. It is similar in habit and appearance to the ragweeds and is 
undoubtedly closely related to them. It has occasionally been suspected of 
causing hayfever (SCHEPPEGRELL 1916a), but is probably of only slight im- 
portance because its pollen is "tenacious and difficult to scrape off even for 
microscopical observation" (KAHN 1924). 

The pollen grains of the Heliantheae (fig. 58F) are typical of the 
family. They are always conspicuously echinate with spines generally long 
and pointed, though there is considerable variation among the members in 
this respect. In the pollen grains of some, particularly the feverfews and 
their close relatives, the spines are short and conical resembling those of the 
Astercae. The exine is moderately thick and finely and faintly granular, 
especially around the spines. The furrows are generally broad, of medium 
length, and tapering to pointed ends, each enclosing a large germ pore 
through which the germinal papilla may bulge prominently. The furrows 
are generally three in number, but may be otherwise. For example, in 
the grains of dahlia they are always six. The pollen grains of both the ordi- 
nary and aberrant Heliantheae have been made the subject of an extended 
investigation by the author (WODEHOUSE 1928&, 1935). 

Ambrosieae: The ragweed tribe is familiar through such well known 
plants as the ragweeds, cockleburs and marshelders. All are wind polli- 
nated, exhibiting extreme simplification of their floral structure in adapta- 
tion to this mode of pollination. The flower heads are always small and 
never showy, and the florets are unisexual. In some cases the staminate 
flowers are clustered in the center and the pistillate on the periphery of the 
same flower heads ; in others the staminate and pistillate flowers are in 
separate heads but on the same plant. 


Oxytenia, Copper weeds 


Iva, Marshelders 


Cyclachaena, Prairie ragweeds 



h Modified from RYDBERG (1922). 

Chapter III 




Hymenoclea, Greasebushes 
Ambrosia, Ragweeds 
Franseria, False ragweeds 
Xanthium, Cockleburs 

This tribe is most closely related to the Heliantheae, merging with it 
through the feverfews of that tribe which bear a remarkable resemblance 
to the ragweeds, except that they are insect pollinated. The Ambrosieae 
should perhaps be regarded as wind pollinated derivatives of the sunflower 
tribe. The pollen grains of all show the typical modifications of response to 
wind pollination, the exine being invariably thinner and the spines shorter 
than in the grains of the Heliantheae. 

Iva (The Marshelders) 

The marshelders are coarse annual or perennial herbs, occasionally 
partly woody, generally rough, with thick opposite leaves or the upper 
alternate, bearing small nodding axillary and solitary, spicate-racemose, or 

FIG. 59. Marshelder (Ira} flowers. A, disk; B, marginal, both greatly enlarged; 
C, flower head, less enlarged. 

paniculate heads of greenish flowers (fig. 59) in the axils of leaf like bracts, 
the staminate in the center of the head with one to six pistillate around the 
margin. All species are entirely wind pollinated, sometimes shedding large 
quantities of pollen which interreacts more or less perfectly with that of the 
ragweeds (PRINCE and SECREST 1939) and is known to cause hayfever in 
regions where they are abundant. 

Their pollen grains are scarcely distinguishable from those of Ambrosia. 
They are 19 to 2\p in diameter and with spines generally slightly less 
prominent than in the grains of Ambrosia. 

The genus comprises about 11 species native of North America. All 
are potential causes of hayfever on account of their mode of pollination, the 
amount of pollen they shed, and its apparently universal character of aller- 
genic toxicity, but only three species can actually be regarded as important 
factors in hayfever. 

Common marshelder or high- water shrub (7. oraria Bart.) is a 
herbaceous or partly shrubby perennial, abundant in tidal marshes along the 

Roger P. Wodehouse 


Hayfever Plants 

Atlantic and Gulf coasts from Massachusetts to Texas. In the southern 
part of its range (south of Virginia) the plants assume a slightly different 
form from those of the northern part, differing in their somewhat narrower 
leaves and slightly smaller flower heads, and are generally known as 
/. frutescens L. The difference between the two forms, however, is scarcely 

FIG. 60. Rough marshelder (/Va ciliata). 

enough to be regarded as specific, and for all practical purposes the two 
names should be regarded as synonymous. The plants flower from July to 
September, beginning and ending their flowering period two or three weeks 
earlier than the ragweeds in the same regions. On account of its restricted 
range and general lack of abundance this species is only a local and occa- 
sional cause of hayfever. 

Chapter III 135 Angiosperms 

Rough marshelder (7. ciliata Willd., fig. 60) is a coarse hispid annual 
with the aspect of ragweed but less branched, about 2 to 6 feet high and with 
its flower heads in long terminal spikes. It is generally found in moist and 
alluvial soil from Illinois to Louisiana and westward to Nebraska and New 
Mexico. It flowers in August and September shedding fairly large amounts 
of pollen which is an important cause of hayfever. 

Poverty weed or small-flowered marshelder (/. axillaris Pursh) is a low 
perennial herb, generally less than 2 feet high with a creeping rootstock, 
flowering from May to September. Its flower heads are small and incon- 
spicuous in the axils of the upper leaves. Though individual plants shed 
only little pollen, they are frequently so numerous that they are an important 
factor in hayfever. They are abundant in saline soils from Saskatchewan 
to British Columbia and southward to New Mexico and California. 


Copperweed (Oxytenia acerosa Nutt.) is a shrubby erect perennial 
occurring in the alkaline plains of the Death Valley region and eastward to 
Arizona and Utah. It is not known to cause hayfever but the plants have 
been shown by SCHWARTZ and WARREN (1940) to cause dermatitis by 
contact. They are said also to be poisonous to stock. 

The pollen grains of copperweed differ from those of ragweed in that 
their furrows are long and their spines well developed, resembling more 
closely the grains of Parthenium (WODEHOUSE 1935). 

Gyclachaena (The Prairie Ragweeds) 

The cyclachaenas are coarse annual herbs with numerous small bractless 
flower heads in panicles, each with 8 to 20 staminate and about 5 pistillate 
flowers, the latter with their corollas represented by a small hyaline ring or 
absent. They are easily distinguished from the marshelders with which 
they are often confused in hayfever literature, by their paniculate bractless 
inflorescence and the reduced corollas of their pistillate flowers. The genus 
comprises four species characteristic of prairie and arid regions of the west- 
ern states and Mexico. All are entirely wind pollinated and produce large 
quantities of pollen of marked hayfever toxicity, but only the following 
species is abundant enough to be considered a factor in hayfever. 

The pollen grains (fig. 58D) of all four species are alike except for slight 
differences in the size and distance apart of their small spines. They may 
easily be distinguished from the grains of Iva and Ambrosia by their ex- 
ceptionally long germinal furrows which are so long that they almost meet 
at the poles of the grain, a character which suggests a considerable genetic 
gap between this genus, and Iva and Ambrosia. 

Prairie ragweed (C. xanthijolia Fresn., fig. 61), also known as bur- 
weed, horseweed and carelessweed, is a tall coarse annual reaching a height 
of six feet or more, with large leaves resembling those of cocklebur in their 
broad form and rough texture. The flower heads are small and numerous 
in terminal naked panicles and axillary spikes. 

Prairie ragweed has much the habit of tall ragweed and, like it, is favored 

Roger P. Wodehouse 


Hayfever Plants 

by disturbed soil, and is frequently abundant in waste places in and about 
settled regions. Its range extends from Illinois to Saskatchewan and Idaho 
and southward to New Mexico, Texas and Missouri. It flowers from July 
to August producing enormous quantities of pollen, sometimes even out- 
ranking that of ragweed, with which it inter reacts more or less perfectly 

FIG. 61. Prairie ragweed plant (Cyclachacna xanthijolia) . 

(FEINBERG and DURHAM 1933), and is one of the most important causes 
of hayfever throughout much of its range. Both its leaves and pollen are 
also known to cause dermatitis (CUNNINGHAM and WOLFE 1932, HUBER 
and HARSH 1932). 

In hayfever literature prairie ragweed is generally known as 'burweed 
marshelder'. Such can only be regarded as a misnomer, probably arising 

Chapter III 



from its unfortunate assignment by some botanists to the genus Iva as Iva 
xanthijolia Nutt, which name is also in common usage. 


Two species of Dicoria are also considered to be possible causes of hayfever in 
the arid regions of the Southwest. One of these, D. canescens Gray, is a spreading an- 
nual herb about one to three feet high, with striate stems, leaves densely white hirsute 
on both sides and long petioled, the lower lanceolate and dentate, the upper oval or 
suborbicular, the flower heads borne in numerous leafy panicles. The staminate and 
pistillate flowers are borne in the same heads, with the paleae subtending the latter 
usually large becoming more than one half inch long in fruit. The plants occur in 
sandy washes of Arizona, southeastern California and southern Utah, especially in the 

FIG. 62. Ragweed (Ambrosia), staminate flower heads and florets. A, B, E, 
flower heads; C, floret just after shedding its pollen; D, floret unopened. 

Colorado and Mohave deserts. The other, D. Brandegci Gray, is similar in appearance 
and habit but may be distinguished by the smaller size of the paleae subtending the 
pistillate flowers, and its oblong-lanceolate or linear leaves. Its distribution is also 
similar, occurring in southwestern Colorado, southern Utah and Arizona. Both species 
appear to have hayfever possibilities but their importance in this respect is not fully 
understood. They are, however, regarded by SELFRIDGE (1918) as important in hay- 

Ambrosia (Ragweeds) 

The ragweeds are coarse annual or perennial herbs with lobed or vari- 
ously dissected leaves. They are distinguished from the marshelders and 

Roger P. Wodehouse 


Hayfever Plants 

prairie ragweeds by having their staminate and pistillate florets on different 
parts of the plant. The staminate heads are nodding in terminal spikes, 
their involucral bracts united, five to fifteen lobed and umbrella like above 
the nodding heads (fig. 62 A, B, E) ; the pistillate heads are borne below 
the staminate spikes, erect, each with but a single floret which is completely 
enveloped by its involucre of united bracts with only a small opening at the 
tip of an apical beak-like projection through which the two-branched style 
may protrude. The involucre of the pistillate head with its single enclosed 
floret is ovoid with its beak surrounded by a single series of tubercles or 
short spines. It is chiefly on these characters that the genus is distinguished 
from the remarkably similar and closely related group of the false ragweeds 
(Franseria) , the involucres of the pistillate heads of the latter being pro- 
vided with more than a single row of tubercles or spines. 

FIG. 63. Ragweed (Ambrosia} seeds. A-C, short ragweed, with their outer 
coats still on ; D, E, their outer coats removed ; F, G, tall ragweed, their outer coats 
still on ; H, its outer coat removed. 

The pollen grains (fig. 58C) are oblate spheroidal, 17 to 24/x in diameter, 
with small and scarcely pointed spines, somewhat various among the dif- 
ferent species. The furrows, generally three or occasionally four or more, 
are short and pit like, almost coinciding in extent with their small enclosed 

Chapter HI 139 Angiosperms 

germ pore. The exine is moderately thick, thicker than that of the grains 
of Xanthium and most species of Franseria, and finely but conspicuously 
granular. These grains are virtually indistinguishable from those of Hy- 
menoclea, Iva, Acanthambrosia, Acanthoxanthium and some species of 
Franseria. They are, however, easily distinguished by their short pit-like 
furrows from the grains of Cyclachaena, Oxytenia, Chorisiva, Dicoria, 
Leuciva and Euphrosyne, all of which have long tapering furrows, and by 
their more prominent spines from the grains of Euxanthium and some 
species of Franseria. Outside of the family, however, there appears to be 
no species with which ragweed pollen grains could be confused. 

The genus comprises 21 species, all entirely wind pollinated and shed- 
ding exceptionally large quantities of buoyant pollen. The pollens of the 
different species appear to interreact more or less perfectly so that sen- 
sitization to that of one of them implies a greater or less sensitization to 
that of the others (PRINCE and SECREST 1939). However, that the anti- 
genie structures of the pollens of the different species are not always iden- 
tical has been shown by CROMWELL and MOORE (1933) in the case of the 
tall and short ragweeds. Though all species are potential causes of hay- 
fever, only the following are abundant enough to be of much importance. 
These appear to owe their great abundance to their extraordinary ability to 
take possession of freshly disturbed or denuded soils, and the longevity of 
their seeds which have been shown (DARLINGTON 1941) to be capable of 
germinating after being buried in sand for 40 years. As a consequence of 
this they are everywhere attendant upon the ravages of an expanding human 
population, especially in the partially settled districts around towns and the 
great cities. 

The classification and nomenclature of the ragweeds followed here is 
that of RYDBERG (1922). 

Short or common ragweed (A. elatior L., A. artemisiijolia T. & G., 
fig. 64) is an annual herb frequently much branched, not more than 4 feet 
high, with rough or somewhat hairy fern like leaves, twice pinnately cleft 
or the upper only once cleft. The staminate flower heads are numerous, 
nodding in long terminal spikes. Their umbrella-like involucres are some- 
what oblique, about 3 mm. wide. The one-flowered pistillate heads are 
borne singly or in small clusters in the axils of the upper leaves, excepting 
occasional plants which are predominantly pistillate in which case they 
largely or entirely replace the staminate heads in the terminal spikes. The 
short ragweed is similar in appearance to the western ragweed but may be 
distinguished by its fibrous annual root (the western species possesses a 
perennial creeping rootstock), and by its generally twice pinnatifid leaves 
(those of the western species are most commonly only once pinnatifid). 

The pollen grains of the short ragweed (fig. 58C) are 17.6 to 19.2/* 
in diameter, with short and rather blunt spines and nearly always three fur- 
rows. They may be distinguished from the grains of the giant ragweed by 
their slightly larger size and their smaller spines, and from those of western 
ragweed by their smaller size and the fact that the pollen of the latter always 
contains a large number of grains with four germinal furrows. 

Roger P. Wodehouse 


Hayfever Plants 

The short ragweed is found almost throughout the United States, ex- 
tending in distribution from the Atlantic to the Pacific through southern 
Canada and as far south as southern Florida and northern California in the 
United States, and in Cuba. Its effective range as a hayfever plant, how- 
ever, is somewhat less, reaching only as far west as Montana and western 

FIG. 64. Short ragweed (Ambrosia elatior), flowering branch. 

Kansas. It flowers from early August to late September throughout most 
of its range, the exact time depending upon latitude; in the northern part 
of its range the plants come into flower several weeks earlier than in the 
southern part, except in the extreme south, the west coast of Florida, 
Louisiana and Cuba, where it flowers from May to September. 

Chapter III 



Short ragweed, as generally understood, is a complex and variable 
species consisting of a number of genotypes (K. L. JONES 1936) which 
jmder natural environmental conditions tend to segregate out. Some of 
:hese have come to the attention of taxonomists and been given specific 
lames. One is A. artemisiifolia L., the form first described by LINNAEUS 

FIG. 65. Tall ragweed (Ambrosia trifida), flowering branch. 

but, as pointed out by FERNALD and GRISCOM (1935), it is easily recog- 
nizable among the progeny of a single plant of A. elatior. The others are 
A. diver sijolia, occurring in Washington and Wyoming, A. media and A. 
longistylis in the Rocky Mountain region, A. Rugelii and A. glandulosa of 
the southern coastal plain and A. monophylla of the Gulf coastal region, the 

Roger P. Wodehouse 142 Hay fever Plants 

Florida keys and Cuba. Only the latter is perhaps worthy of specific 
recognition since it has the peculiarity of flowering off season, in May and 
June as much as in August and September (WODEHOUSE 1942a). Mor- 
phologically it is well within the normal range of variation of the progeny 
of A. elatior. 

Tall ragweed or giant ragweed (A. trifida L., fig. 65) is a coarse branch- 
ing annual, reaching 15 feet in height, with rough stems and leaves. The 
latter are broad, three or five cleft or entire on rather long petioles which 
are more or less winged on their margins. The staminate heads are numer- 
ous, larger than those of the short ragweed, borne in long terminal spikes. 
The pistillate are similar to those of the short ragweed but larger, borne in 
small clusters at the base of the staminate spikes in the axils of three cleft 

The pollen grains of tall ragweed are similar to those of the short species 
but may be distinguished by their smaller size, 16.5 to 19.2/ut in diameter, 
and their slightly more prominent spines. 

In distribution the tall ragweed extends from Quebec to North Carolina 
and west to Colorado and British Columbia, but its effective range as a 
cause of hayfever does not extend west of the Dakotas, Nebraska and Kan- 
sas. It is generally found in disturbed soil, such as along the banks of 
streams, on flood plains (GEDDES 1875), roadside ditches, improperly culti- 
vated farm land and vacant lots. It flowers at about the same time as the 
short ragweed, but generally starting a few days earlier, and throughout 
most of its range the pollens of the two species, which interreact almost per- 
fectly, act together in causing hayfever so that it is not possible to tell to 
which species to credit the greater responsibility. On the whole the dwarf 
ragweed is the more widely distributed, more universally abundant and 
credited with the greater toxicity, but in many regions the giant far outranks 
the dwarf in the number of individuals, size of the plants and amount of 
pollen produced. 

The giant ragweed is less tolerant of drought than the short ragweed 
and more readily invades the moister regions. Its seed (fig. 63) is partly 
aquatic in that its fibrous coat is only slowly penetrated by water, permitting 
it to be carried great distances by rivers and streams. This explains its 
presence along river banks and freshly silted flood plains. FOERSTE (1882) 
tells of another way in which its seeds may be distributed. He states that 
five or six strands of ice, one and a half to three inches long become attached 
to the beak and protuberances of the achene and these enable the seed to be 
carried away by the wind. I have not seen this phenomenon, but I have not 
looked for it in Dayton, Ohio, where he reports its occurrence. 

Western giant ragweed or Texas great ragweed (A. apt era DC.) is very 
similar and closely related to the eastern giant ragweed ; in fact it is some- 
times regarded as merely a variety of the former (A. trifida texana Scheele). 
It can, however, be distinguished from the eastern form by its more sturdy 
habit of growth, its tendency to branch higher up, its more deeply cut leaves 
with their petioles wingless. All of these characters are somewhat various 
and, while convenient in the field, are not entirely reliable. The two forms 

Chapter III 



may, however, also be distinguished by their fruits ; those of the giant rag- 
weed are slightly if at all pitted between the ridges and the latter end in short 
conic spines ; while those of the western giant ragweed are more markedly 
pitted between the ridges and these end in only small tubercles or the seeds 
are unarmed. 

The pollen grains are exactly the same as those of the eastern form. 

In distribution the western giant ragweed is limited to the southwestern 
part of the United States from Louisiana to Arizona and adjacent Mexico. 
It flowers in late summer shedding quantities of pollen as great or greater 
than the eastern giant ragweed and in regions where abundant causes much 
hayfever. In hayfever studies the two species of giant ragweed are seldom 
distinguished from each other, both going by the name of A. trifida. 

FIG. 66. Southern ragweed (Ambrosia bidentata}. A, B, Staminate heads; C, 
Flowering spike. 

Southern ragweed (A. bidentata Michx., fig. 66), also called lance- 
leaved ragweed, is a rough branching annual, 1 to 3 feet high with hairy 
sessile leaves, generally with one large central lobe flanked by two smaller 
lanceolate lobes or teeth on each side. The staminate heads are numerous, 
sessile in dense terminal spikes, their involucres extremely oblique with a 
conspicuous and reflexed lanceolate lobe on the inner side. The pistillate 
heads are few borne singly or in clusters in the axils of the leaves below. 

The pollen grains are similar to those of the giant ragweed but may be 
distinguished by their larger size (19.8 to 21/x in diameter). 

In distribution the southern ragweed is restricted to prairies from south- 
ern Illinois to Louisiana and westward to Texas and Nebraska, and its 

Roger P. Wodehouse 144 Hay fever Plants 

effective range is further restricted, not extending west of Kansas and Okla- 
homa. In this area it is regarded as a local cause of hayfever from July to 
September but it is scarcely comparable with the other species already men- 

Western ragweed (A. psilostachya Gray) is a perennial herb with creep- 
ing rootstocks and simple erect stems, generally only 1 to 4 feet high or 
occasionally higher. The leaves are rough hairy mostly once pinnately 
divided though the lower may be twice divided. This species closely re- 
sembles the eastern short ragweed and, like it, is favored by disturbed soil. 
"Abandoned fields, vacant lots, roadsides and railway embankments are its 
usual haunts" (ABRAJVIS 1932). It is also often particularly abundant along 
irrigation ditches, but is seldom as abundant as the short ragweed in the 
East. In distribution it ranges from California, Idaho and Saskatchewan 
eastward to Illinois and Louisiana. It may flower from June to December, 
varying with the locality, but in most places it flowers only in September and 
October. It sheds large quantities of pollen which is the cause of much 
hayfever but on account of the more localized occurrence of the plants and 
their smaller size this is less important in hayfever than the pollen of the 
tall and short ragweeds. 

The pollen grains of the western ragweed are similar to those of the 
eastern giant ragweed, with spines somewhat larger and more pointed than 
in the grains of the short ragweed. They also differ in their larger size, 22 
to 24.7/x in diameter, and in the fact that nearly half of the grains have four 
instead of the usual three germinal furrows. Though the pollen grains are 
slightly larger than those of the other species mentioned, they are still quite 
small enough to be carried freely in the air. 

The species occurs in several slightly different forms which are regarded 
by some taxonomists as different species (RYDBERG 1922), as A. coronopi- 
folia T. & G., A. calijornica Rydb., and A. psilostachya DC. For purposes 
of hayfever studies, however, such taxonomic refinements are neither neces- 
sary nor desirable, and these names may be treated as synonyms. 

Among the remaining members of the genus several others are occasionally men- 
tioned as possible causes of hayfever, and, indeed, it is quite possible that some of them 
may be local factors, but they lack the weedy habit of invading freshly denuded territory 
which is the chief characteristic which leads to the present abundance of those already 
mentioned. Among the species of secondary or doubtful importance are the seashore 
ragweed (A. hispida Pursh), a low prostrate creeping perennial herb with white hairy 
leaves their blades twice pinnately cleft. It commonly occurs only on sea beaches and 
coastal dunes of Florida, Cuba, the Bahamas and Central America where it serves as a 
sand binder. It is suspected of contributing to the ragweed pollen in the air in parts 
of Florida (DURHAM 1933b). It flowers almost throughout the year but appears to 
be of little or no consequence in hayfever, probably because of its local distribution, 
also because it is still growing in normal balanced relation to its environment, unin- 
fluenced by human activity. 

Another species which is sometimes mentioned in hayfever literature is the dwarf 
or Tiajuana ragweed (A. pumila Gray). It is a low and inconspicuous weed with 
small finely dissected grayish leaves. According to ABRAMS (1932), "It inhabits lower 
California and reaches its northern limit in southern San Diego County, California, 
where it may be a local factor". 

Chapter III 145 Angiosperms 

Franseria (False Ragweeds) 

The false ragweeds are similar and closely related to the true ragweeds 
and to the cockleburs, constituting a chain of connecting links between these 
two genera. Their chief distinguishing characters are found in the in- 
volucres of the pistillate heads ; these, instead of having only a single circle 
of tubercles or spines as in the ragweeds, are provided with several series, 
the fruits developing into a bur at maturity, in some cases similar to that of 
the cockleburs. In some species the pistillate heads are one flowered and 
one beaked, as in the ragweeds (fig. 69), in others they have a larger number 
of flowers and a correspondingly larger number of beaks up to eight, even 
more than the cockleburs. 

The pollen grains of most species are similar to those of the ragweeds, 
while those of others have only vestigial spines like those of most cockleburs. 

The genus comprises about 39 species of annual or perennial herbs or 
low shrubs, principally of western distribution. Though they have the same 
hayfever proclivities as ragweeds and their pollen interreacts with that of 
the ragweeds more or less perfectly, they are much less important in hay- 
fever because they are less common and less widely distributed. 

Bur ragweed (F. acanthicarpa Cov., Gaertneria acanthicarpa Britt., fig. 
69) is a diffusely branching hirsute annual generally with stems 1 to 2 feet 
high, similar in appearance to short ragweed. The staminate heads are loosely 
arranged in numerous paniculate racemes, the pistillate heads one flowered 
in small clusters in the upper axils. These at maturity are armed with 
numerous long flat straight spines. 

The pollen grains are 18.7 to 20.3/A in diameter similar to those of short 
ragweed but with their spines slightly less prominent. 

Bur ragweed is a natural inhabitant of sandy plains and valleys and 
summer beds of winter flood streams. It is also specially common in culti- 
vated and waste grounds throughout the United States principally west of 
the Mississippi River and adjoining parts of Canada, and in many places is 
the commonest weed of cultivated fields. It flowers from July to October 
shedding large amounts of pollen which in many parts of its range is one 
of the worst causes of hayfever. On account of its spiny fruits and pref- 
erence for sandy soils it is sometimes called sandbur. 

Slender ragweed (F. tenuifolia Harv. & Gray, Gaertneria tenuifolia 
Ktze., fig. 67) is an erect perennial herb closely resembling western ragweed, 
1 to 2 feet high with rough stems and leaves, the latter interruptedly bi- or 
tri-pinnatifid with the divisions narrow, the terminal one often elongate. 
The staminate heads are about 3 mm broad, their involucres dark brown 
with three blackish ribs, loosely arranged in narrow paniculate spikes. The 
pistillate heads are borne in small clusters in the upper leaf axils 1 or 2 
flowered, developing at maturity into a bur with stout hooked spines. 

The pollen grains are similar to those of the giant ragweed but somewhat 
larger, 19.8 to 20/A in diameter. 

Slender ragweed "grows in warm dry districts from the westerly part 
of the Mississippi Valley to Colorado, Nevada and southern California, and 

Roger P. Wodehouse 


Hayfever Plants 

ranges south to Texas" (HALL in SCHEPPEGRELL 1917 a). It flowers from 
July to October shedding fairly large amounts of pollen. Throughout most 
of its range it appears to be much less important than other members of the 
ragweed tribe, but in parts of Arizona it is counted among the most im- 
portant causes of hayfever and is rapidly becoming more so (PHILLIPS 

FIG. 67. Slender ragweed (Franseria tenuifolia), part of a flowering plant. 

Canyon ragweed, rabbit bush, Arizona bur sage (F. deltoidea Torr., 
Gaertneria deltoidea Ktze.) is a shrubby perennial with finely tomentose 
branches, of arid regions in southern Arizona and Mexico. It flowers in 
early spring, and is reported by ABRAMS (1932), WATSON and KIBLER 
(1922) and PHILLIPS (1932) as an important cause of hayfever in Arizona. 

Chapter III 147 Angiosperms 

Its pollen grains are similar to those of cocklebur with vestigial spines, 
20 to 22/i in diameter. 

The desert bur sage, burrow weed or sand bur (F. dumosa Gray, Gaert- 
neria dumosa Ktze.) is a low grayish shrub, not more than 20 inches high 
with rigid branches terminating in spicate inflorescences which become in 
the second year naked hardened spines. It grows in great abundance in the 
Colorado and Mohave deserts, its range extending eastward to Utah and 
southward into Mexico. It flowers from about March 10 to June when the 
hot weather begins, and is known to be a severe cause of hayfever in Arizona 
(PHILLIPS 1932). 

Sonora bur sage or canyon ragweed (F. ambrosioides Cav.) is a shrubby 
perennial with large spiny burs and broad petioled leaves, with something 
of the appearance of a cocklebur, occurring in desert areas of Arizona, 
Mexico and Lower California. It flowers from March to May, and is re- 
garded as important in hayfever (ABRAMS 1932, PHILLIPS 1932). 

Among the remaining species of Franseria several are regarded as possible causes 
of hayfever but at their worst they could only be local contributors on account of their 
lack of abundance and restricted distribution. Such a one is the low ragweed (F. dis- 
color Nutt). It is a low perennial herb with creeping rootstock, irregularly bipinnati- 
fid leaves, white tomentose beneath. It occurs on plains from South Dakota and 
Nebraska to New Mexico, Arizona and Wyoming. Another is the beach sandbur (F. 
bipinnatifida Nutt.). It is a low spreading perennial herb with leaves twice or thrice 
pinnatifid and long prostrate running stems with their ends turning abruptly upward and 
ending in a spike of staminate flower heads. It is common on sea beaches and sand 
dunes where it acts as a sand binder, from Lower California to British Columbia. It 
flowers from April to December, and is reported to be an important local cause of hay- 
fever (RowE 1928). Often associated with it is the less common but similar and closely 
related false ragweed (F. Chamissonis Less.). This may be distinguished from the 
preceding species by its leaves which are merely serrate or the lower incised. 

Xanthium (The Cockleburs) 

The cockleburs are coarse annual weeds with widely branching stout 
stems and petioled lobed leaves (fig. 68). The flower heads are unisexual ; 
the staminate greenish, subglobose, with involucres of slender and entirely 
separate bracts, arranged in terminal spikes above the pistillate heads, the 
latter two flowered, occasionally one or three flowered, with united and 
closed involucres tipped by as many beaks as there are flowers and maturing 
into one to three seeded stout indurated burs, copiously armed with hooked 

The genus comprises about 20 species of world wide distribution but 
mostly American. These fall naturally into two sharply distinguished sec- 
tions, Euxanthium and Acanthoxanthium, those of the latter distinguished 
by conspicuous tripartite spines borne on the stem at the base of the leaves. 
Such spines are lacking in all species of Euxanthium (MILLSPAUGH and 
SHERFF 1922). 

The pollen grains of Euxanthium section (fig. 58E) are spheroidal about 
22.1 to 29. 1/x. in diameter with spine vestiges generally scarcely apparent, 
2 to 2.8/i apart. Their furrows are generally three, very short, merely pits 
in the exine ; the latter is thin and finely granular. The grains of the species 

Roger P. Wodehouse 


Hayfever Plants 

of the Acanthoxanthium section are essentially the same as those of short 
ragweed, 19 to 22/u, in diameter and with low spines, 3.4 to 5.1/i apart. In 
some classifications the two sections are regarded as separate genera; the 
great difference in the appearance of the plants and their pollen grains sug- 
gest that there is ample justification for this separation. 

The cockleburs are mostly weeds of waste places, roadsides, neglected 
farms and railroad embankments where they often grow in great profusion, 
but most species shed so little pollen that they are relatively unimportant 

FIG. 68. Cocklebur (Xanthium), plant and seeds. 

in hayfever even where the plants are abundant. Exceptional in this respect 
is the great clotbur (X. speciosum Kearney). It is a large robust and ex- 
ceedingly coarse and bushy plant, 3 to 4*^ feet high with burs 1 inch long 
or more, provided with numerous curved prickles, themselves spiny, and 
two long hooked beaks. This species is common in waste ground especially 
where moist, throughout the Great Plains region and Mississippi Valley. 
It flowers in August and September and appears to shed much more pollen 
than most other species. 

Of the other species of this genus the commonest and most widely dis- 
tributed is the Pennsylvania cocklebur or clotbur (X. pennsylvanicum 

Chapter III 



Walr.) a similar but less robust species. It is common in waste places 
practically throughout the United States and parts of Canada and Mexico. 
This species is frequently encountered in the literature under the name 
X. canadense Mill., which is a misnomer. Undoubtedly other species are 
involved in hayfever but they are seldom differentiated. Indeed it appears 
unnecessary to differentiate them as far as concerns the members of the 
Euxanthium section of the genus, for the pollens of the various species 
appear to interreact perfectly with each other, and almost perfectly with 
those of the ragweeds (FEINBERG and DURHAM 1933). The California 
spiny or thorny clot bur or clotweed (X. spinosum L.) is the only member 
of the Acanthoxcmthium section of the genus found in America. It is 
erect spreading much branched, 1 to 3 feet high with numerous pointed 
leaves dark green above and white canescent below. The stem is armed 
with sharp tripartite spines. It is naturalized from Portugal, almost through- 
out the United States but apparently only in California is it abundant enough 

FIG. 69. Bur ragweed (Franseria acanthicarpa) . A, Staminate head; B, Stam- 
inate floret; C, Pistillate head with the style branches of its single floret protruding. 

to be a factor in hayfever. Even there it is probably unimportant, for the 
plants yield pollen only sparingly. It flowers from August to November. 

Hymenoclea (Greasebushes) 

Of less importance in hayfever are the greasebushes, H. Salsola T. & G. 
and H. monogyra T. & G. These are desert shrubs with narrow linear 
leaves, with flowers and inflorescences quite like those of the ragweeds, but 
the involucres of the pistillate heads have 6 to 12 dilated scarious blade like 
transverse wings. The former species, which is known as burrowed or 
romerillo is found in saline soils in Arizona and adjoining parts of Utah, 
Nevada and California. It flowers in spring, and is regarded as important 
in parts of California and Arizona (SELFRIDGE 1918, ABRAMS 1932, PHIL- 
LIPS 1932). The latter, known as Jecote, is found from California and 

Roger P. Wodehouse 150 Hayfever Plants 

Nevada to eastern Texas. It flowers in late summer and is regarded as of 
secondary importance in Arizona (WATSON and KIBLER 1922). 

Helenieae : The sneezeweed tribe is a small group of plants similar and closely 
related to the Heliantheae. It is best known to us through such garden flowers as the 
marigolds (Tagetes), gaillardias and sneezeweed (Helenium}, the latter occasionally 
suspected of causing hayfever. The odor of marigolds (Tagetes) has recently been 
stated to cause hayfever symptoms even in the absence of pollen (BIEDERMAN 1937). 

Arctotidae: The African daisy tribe is almost entirely South African, known 
only in America through a few cultivated forms like the African daisy (Arctotis 
grandis Thunb.) which closely resembles the ox-eye daisy except that the florets of the 
disk are blue. 

Calenduleae : The calendula tribe is the smallest and most compact of the family 
with about 100 species in 8 genera, almost entirely South African. It is best known in 
America through the Cape marigolds (Dimorphotheca) from South Africa and the 
calendula or pot marigold (Calendula officinalis L.), a common flower-garden annual 
from the Mediterranean region. It is improbable that any of these could be of any im- 
portance in hayfever. 

Inuleae: The inula tribe is familiar to us through such forms as the everlastings 
(Antennaria, Gnaphalium and Anaphilis) and the straw flower (Plelichrysum). 

It is unlikely that any of them could ever be of any importance in hayfever for they 
are entirely insect pollinated and shed but little pollen. 

Astereae: The aster tribe comprises over 1400 species distributed 
in about 90 genera which are so closely related to each other that it is difficult 
to draw their limits. The tribe is familiar to us through such forms as the 
asters, goldenrods, fleabanes (Erigeron), cultivated asters (Callistephus) 
and English daisy (Bellis). Though most of them appear to be entirely 
insect pollinated, some shed much more pollen than is carried off by insects, 
and this may become a menace to hayfever sufferers from handling the 
plants. Or even the pollen may occasionally become atmospheric to a small 
degree ; such is known to be the case with some of the goldenrods and flea- 
banes. Those who have attempted to collect goldenrod pollen have often 
been convinced by the meagreness of the results that goldenrods shed too 
little pollen to be important in hayfever. For most species this is quite true. 
Of sixteen species which were tested for their pollen yield, only two, the 
noble goldenrod (Solidago speciosa Nutt.) and the seaside goldenrod (S. 
sempervirens L.) could be made to yield pollen in collectable quantities. 
The yields from these two are quite generous. Furthermore, their pollen 
can often be detected in the air several miles from the fields when the plants 
are in flower. 

In Baccharis the flowers are dioecious and appear to be at least partly 
wind pollinated. The species of this genus are mostly South American, 
several are found in North America, and one, the groundsel bush (B. halimi- 
jolia L.) is common wild and occasionally cultivated in the United States. 
It occurs naturally along sea beaches and in salt marshes from Florida to 
Texas and less abundantly along the Atlantic coast as far north as Massa- 
chusetts. It is probably a local cause of hayfever. Indeed it is reported as 
such in parts of Florida (NICHOL and DURHAM 1931). It flowers in the 
late summer at about the same time as or later than the ragweeds. 

The pollen grains of the aster tribe are extremely uniform throughout 
the group, so much so that it is generally impossible to tell those of one 

Chapter III __ 151_ Angiosperms 

genus from those of another (fig. 58G). They are 16 to 32/n in diameter, 
with finely granular exine, and provided with low conical spines. The fur- 
rows are long and tapering, each with a germ pore. Though characteristically 
three in number throughout the group, there is a marked tendency towards 
furrow proliferation. These grains with supernumerary furrows have 
been made the subject of extended studies by the author (WODEHOUSE 
1930, 1935). 

Vernonieae : The members of the ironweed tribe are characterized 
by having the florets all perfect and tubular, those of the margin of their 
heads rarely differing noticeably from those of the center. The tribe com- 
prises the huge genus of ironweeds (Vernonia) with more than 500 species, 
principally South American (GLEASON 19230, b), and about 25 smaller 
genera which are scarcely represented in the United States outside of cul- 
tivation (GLEASON 1922). The best known example is Stokes' aster 
(Stokesia laevis Greene), a beautiful garden perennial with large heads of 
sky-blue or white flowers in summer. All are insect pollinated and their 
pollen sticky, so that none could possibly be regarded as a cause of hayfever, 
though the ironweeds have occasionally been mentioned in hayfever litera- 

The pollen grains of the Vernonieae are unlike those of most Composi- 
tae; the exine is thrown into vertical spine-topped ridges describing elab- 
orate and characteristic patterns over the surface as in the grains of the 
Cichorieae, except that their patterns are more complex. These grains have 
been made the subject of investigation by the author (WODEHOUSE 1928a). 

Eupatorieae : The boneset tribe is a distinct group of closely related 
forms, with heads of florets all alike, perfect and tubular. They are best 
known to us through the purple joe-pye-weed (Eupatorium purpureum 
L.) so conspicuous an ornament of late summer woods and meadows, the 
common thoroughwort or boneset (E. perjoliatum L.) and the blazing stars 
(Liatris or Lacinaria). Stevia (Piqueria trinervia Cav.) with its minute 
delicate white flower heads is used by every florist to enhance the beauty of 
other flowers in assembling bouquets. This plant has been shown to occa- 
sionally cause hayfever among florists and greenhouse workers. Such a 
case is reported by LANGLEY (1937). Their pollen grains are typical of the 
family, generally small, ranging from about 14 to 25/* in diameter, with 
three meridionally arranged furrows long and tapering to pointed ends. 
Their spines, however, are always small, generally smaller even than those 
of the grains of the asters and goldenrods. 

Anthemideae : The mayweed tribe is a group of about 650 species in 
40 genera. Most are insect pollinated and of little consequence in hayfever. 
Others are wind pollinated and of the utmost importance. The former are 
best known to us through such forms as the garden chrysanthemums, ox-eye 
daisy (Chrysanthemum Leucanthenmm L.), the chamomiles (Anthemis). 

Roger P. Wodehouse 


Hayfever Plants 

yarrow (Achillea Millifolium L.), tansy (Tanacetum vulgar e L., fig. 70A) 
and pyrethrum. The latter, as occurring in insecticides, is occasionally a 
severe cause of hayfever and asthma. These reactions are believed to be 
independent of the insecticidal part of pyrethrum powder which consists of 
complicated esters (RAMIREZ 1930). Pyrethrum powders have also been 
shown to cause dermatitis (SULZBERGER and WEINBERG 1930), likewise 
the leaves of common tansy (GREENHOUSE and SULZBERGER 1933) and of 
chrysanthemum (GOLDSTEIN 1931). The pollen grains of the entomophilous 
members of the tribe are typical of the family, characterized by their thick 
and coarsely granular exine, provided with broad short conical spines (fig. 

FIG. 70. Tansy (Tanacetum} (left) and Artemisia. Comparison of entomophilous 
and anemophilous flowers which are closely related. 

58 I). The furrows are generally three, of medium length and tapering to 
pointed ends. 

The wind pollinated members comprise the genus of mugworts, sage- 
brushes and wormwoods (Artemisia, fig. 70B) and several smaller related 
genera. Some of these are our worst hayfever plants, described below. 
Among the pollen grains of the wind pollinated members (e.g. Artemisia, 
fig. 58H), the spines are greatly reduced or entirely absent and the exine 
much thinner, but always with its distinctive coarse granular character. 

Chapter III 153 Angiosperms 

Artemisia (Sagebrushes, Mugworts and Wormwoods) 

The artemisias are annual or perennial herbs, or shrubs, usually aro- 
matic and bitter, the annual species generally with a deep tap root and the 
perennial with rootstocks or woody base. The leaves are alternate in 
arrangement and enormously various in the different species. The flower 
heads (fig. 71) are small, nodding or erect in panicles or raceme like 
spikes, the marginal flowers (reduced rays) pistillate and fertile or absent, 
the disk flowers bearing both stamens and pistil or only stamens. 

All species are entirely wind pollinated and most of them copious pollen 
shedders. Next to the ragweeds, and possibly the grasses, they constitute 
the most important group of hayfever plants. 

Many species are extremely variable so that the dividing lines drawn 
between them are often arbitrary, and the group presents taxonomic dif- 
ficulties not encountered elsewhere among hayfever plants. Fortunately, 
however, the American species have been exhaustively studied and reported 
on in two great taxonomic works (RYDBERG 1916, HALL and CLEMENTS 
1923). The authors of these take diametrically opposite views as to the 
limitation of species. RYDBERG recognizes 120 species, after eliminating five 
which he transfers to other genera, while HALL and CLEMENTS recognize 
only 29, including the five rejected by RYDBERG. In RYDBERG'S work vir- 
tually all forms which have ever had names attached to them are given 
specific rank, however slight the differences between them may be, while in 
HALL and CLEMENTS' work a large proportion of these have been reduced 
to subspecies or regarded as varieties, minor variations or synonyms of the 
few quite definitely delimited species. This latter treatment is the more 
suitable to hayfever studies because the allergenic differences between the 
pollen of even the most distinct species appear to be slight or negligible. 
Moreover the work of HALL and CLEMENTS in its clarity, consistency and 
completeness is perhaps the most perfect example of taxonomic work pro- 
duced in modern times. So, in this discussion I have largely followed their 
work. In nomenclature, however, I have given preference to the names 
which are most commonly encountered in hayfever literature, but always 
with the equivalents of HALL and CLEMENTS when these are different. In 
this way I have recognized as species a number of different forms which by 
HALL and CLEMENTS are accorded only the rank of subspecies or varieties. 
This is a concession to custom. For example, the four species, Artemisia 
camporum, A. caudata, A. canadensis and A. pycnocephala are so much 
alike in their essential characteristics and so closely related that HALL and 
CLEMENTS regard them as subspecies of A. campcstris, and it is practically 
certain that there are no observable allergenic differences between their 
pollens, so they had much better be regarded as merely varieties of one 
species. Still all have appeared in hayfever literature as separate species 
under the above names. So, rather than go against the trend and risk greater 
confusion than already exists, I have so treated them. Their interrelation- 
ships, together with their relationships to the other species of the genus 

Roger P. Wodehouse 


Hayfever Plants 

under the broader specific conception, however, are clearly brought out by 
the summary of species below. 

The artemisias are probably to be regarded as wind pollinated derivatives 
of the tansies. There are few constant characters, except those obviously 
due to anemophily, by which the two genera may be distinguished. 

The pollen grains of Artemisia are oblately spheroidal, 17.5 to 28.5/x in 
diameter, provided with normally three furrows which are long and taper- 
ing to pointed ends, their margins sharply defined, their membranes smooth 
and each provided with a well marked central pore. Their exine is thick 
and of the same peculiar coarse granular texture which is found in the grains 
of other Anthemideae, but the spines are represented by only the merest 
vestiges or are entirely absent. The grains of all members of the genus are 
essentially alike except for slight variations in their size and the prominence 
of their spine vestiges when present. These differences, however, are too 
slight to be conveniently used in their identification. This matter is dis- 
cussed at greater length elsewhere ( WODEHOUSE 1926, 1935). 


A. Abrotanum L. 

A. calif ornica Less. (Crossostephium calif ornicum Rydb.) 

A. vulgaris L. (A. vulgaris typica H. & C.) 

A. heterophylla Nutt. (A. vulgaris heterophylla H. & C.) 

A. ludoviciana Nutt. {A. vulgaris ludoviciana H. & C. 

A. gnaphalodcs Nutt. (A. vulgaris gnaphalodes H. & C.) 

A. serrata Nutt. (A. vulgaris serraia H. & C.) 

A. Wrightii Gray (A. vulgaris Wrightii H. & C.) 

A. biennis Willd. 

A. annua L. 

A. Bigelovii Gray 

A. Absinthium L. 

A. frigida Willd. 

A. dracunculoides Pursh. (A. dracimculus glauca H. & C.) 

A. camporum Rydb. (A. campestris pacifica H. & C.) 

A. caudata Michx. (A. campestris caudata H. & C.) 

A. canadensis Michx. (A. campestris borealis H. & C.) 

A. pycnocephala DC. (A. campestris pycnocephala H. & C.) 

A. filifolia Torn 

A. spinescens D.C. Eat. 

A. tridentata Nutt. 

A. vulgaris 






Southernwood (A. Abrotanum L.), also called old man, and garden 
sagebrush, is a pleasantly scented shrub, resembling the coast sagebrush, 
\y 2 to 5 feet high, with green and glabrous leaves with filiform divisions, 
much branched, erect or spreading and forming rounded bushes. The 
species is native of Europe but is much grown as an ornamental shrub in 
American gardens where it is hardy as far north as southern Canada. In 
Canada it is used as a windbreak and in Colorado as a nurse crop in re- 
forestation. It is also frequently escaped in waste places. It flowers in 
August and October, and is regarded as a probable cause of hayfever in 
Minnesota and the eastern parts of the Dakotas where it is sometimes used 
as a hedge plant (ELLIS and ROSENDAHL 1932). 

Coast sagebrush (Artemisia calif ornica Less., Crossostephium calif or- 
nicum Rydb., fig. 71), also called California sagebrush, old man and various 

Chapter III 155 Angiosperms 

other less appropriate names, is a rounded shrub with woody trunk, 2]/ 2 to 4 
feet high, and grayish leaves finely divided into linear segments. 

Coast sagebrush is confined in distribution to the coastal strip of Cali- 
fornia, Lower California and adjacent islands, and is often extremely abun- 
dant on exposed slopes of hills, from 10 to 2500 feet elevation. Throughout 
much of this range it is associated with California mugwort. Flowering 
throughout the latter part of summer, it is reported to be a serious cause of 
hayfever (RowE 1928, SELFRIDGE 1920, HALL 1917) and appears to be 
increasingly so. Of it HALL and CLEMENTS (1923) say: "The foliage is 
not regularly browsed by cattle, because of the strong odor and bitter taste, 
and, although browsed by sheep and goats, this is done only in the absence 
of more palatable food. As a result the hillsides of western California are 
in many places covered with a dense stand of this brush where more de- 
sirable species have been destroyed by sheep, goats and donkeys". It has 
been assigned to the genus Crossostephium by RYDBERG, but its pollen 
grains are typically those of Artemisia, lacking the vestigial spines which 
characterize the grains of the other species of Crossostephium. 

The Vulgaris Group: The following six species are so similar and 
closely related that HALL and CLEMENTS (1923) regard them as merely 
varieties or subspecies of the common mugwort (Artemisia vulgaris L.). 
They are herbaceous perennials, sometimes shrubby at the base, from a 
creeping rootstock, and with a peculiar pungent odor. Their stems are erect 
and mostly unbranched up to the inflorescence, striate or shallowly grooved 
and tinged with red in age. The leaves are enormously various in shape, 
but always white-tomentose beneath and frequently also above. The in- 
florescence is usually a broad panicle, the flower heads small with four to 
ten marginal flowers which are pistillate, and 3 to 50 disk flowers which 
bear both stamens and pistils. 

The group is extremely various, some 80 different forms having been 
distinguished. Of these HALL and CLEMENTS (1923) recognize 15 distinct 
enough to merit subspecific rank. The following six are of special interest 
in hayfever studies. HALL and CLEMENTS state: "Preliminary studies in- 
dicate that the pollen of the different subspecies all react alike. Therefore, 
in testing and treating hayfever cases, the specialist need pay no attention 
to the complicated series of subspecies and minor variations". Many of 
these, however, have already found their way into the hayfever literature as 
separate species, so must be given attention here. 

Common sage wort or mugwort (Artemisia vulgaris L., Artemisia vul- 
garis typica H. & C.) is a stout perennial herb, with erect stems 1 to 
3yi feet high arising from a creeping rootstock. The leaves are exceed- 
ingly various 1 to 4J^ inches long, deeply pinnatifid into linear oblong 
or somewhat spatulate pinnatifid toothed or entire lobes, densely white 
tomentose beneath and dark shining green above. The heads are small and 
numerous, erect, in panicles of simple or compound spikes. 

Common mugwort is native of Europe and Asia. Introduced into 
America it is now found widely scattered from Newfoundland to Georgia 

Roger P. Wodehouse 


Hayfever Plants 

and westward to Alabama, Wisconsin and Manitoba. It flowers from July 
to October, shedding fairly large amounts of pollen but is seldom abundant 
enough to be of much importance in hayfever. 

California mugwort (Artemisia heterophylla Nutt., Artemisia vulgaris 
heterophylla H. & C.) is very closely related and similar to the pre- 
vious species, except that the leaves are less divided and broader, the prin- 
cipal leaves with a few prominent lanceolate lobes, varying to entire ; like 
those of the foregoing species they are white-tomentose beneath and green 
above. But the flower heads are slightly larger. 

California mugwort is common in the northeastern Rocky Mountain 
section from Saskatchewan to Idaho and on the Pacific coast from British 
Columbia to Lower California, and is the most abundant species in Oregon 
and California where it is the characteristic form of the bunch-grass prairies, 
but in California it has largely disappeared with the native grasses since it 

FIG. 71. Coast sagebrush (Artemisia calif ornica) . 
ginal floret; C, Disk floret. 

A, Flowering spike ; B, Mar- 

forms an important part of the late fall and winter feed for all classes of 
stock, especially sheep. 

Dark-leaved mugwort, or prairie sage or wormwood (Artemisia ludovi- 
ciana Nutt., Artemisia vulgaris ludoviciana H. & C.), also called white 
sagebrush, is closely related and very similar to the two preceding species, 
except that the principal leaves are entire or variously toothed, rarely 
divided, and when so the lobes are short, their upper surface more thinly 
tomentose than the lower or at length becoming smooth and green. The in- 
florescence is an elongate narrow compact panicle, the heads more or less 
nodding, 12 to 20 flowered. 

Prairie sage is abundant and widely distributed in western North 
America from Montana to Wisconsin, Kansas, Texas, Chihuahua, Cali- 
fornia, Washington and Idaho. It flowers from August to November and is 
known to cause much hayfever. The name, prairie sage, is less applicable 

Chapter HI 157 Angiosperms 

to this than to the next species, since it is "more typical of the foothill por- 
tions of the mixed prairie and runs high up in the great mountain parks, 
such as Estes Park", where on account of its shade tolerance it forms a 
ground cover in yellow pine woodland. 

Prairie sage, western mugwort, or cudweed (Artemisia gnaphalodes 
Nutt, Artemisia vulgaris gnaphalodes H. & C.) is similar to the pre- 
ceding species, so much so in fact that it is often included with it. It differs, 
however, in that its leaves are heavily tomentose on both sides, but this is 
almost the only constant distinguishing character. It is found in somewhat 
drier and less shaded positions, flowering at about the same time, and is the 
most characteristic sage of the true prairies. It is fairly abundant from On- 
tario and Michigan to Missouri, Texas, Coahuila, California, British Co- 
lumbia and Saskatchewan. 

Sawleaved mugwort or wormwood (Artemisia serrata Nutt., Artemisia 
vulgaris serrata H. & C., A. ludoviciana serrata H. & C.) is similar to 
the other members of the vulgaris group but distinguished by having 
lanceolate or linear-lanceolate pointed leaves with closely and rather evenly 
serrate margins. They are smooth and green above and white-tomentose 

The sawleaved mugwort is restricted in distribution to the northern 
and central portions of the Mississippi valley where it is common and known 
to be an important cause of late-summer hay fever (ELLIS and ROSENDAHL 
1933). It grows in good and rather moist soil, and is a larger plant than 
most of the members of this group, reaching a height of 10 feet. Though it 
is perhaps the most distinct of this group, it intergrades into both A. ludovi- 
ciana and A. gnaphalodes. 

Gray sage (Artemisia Wrightii Gray, A. vulgaris Wrightii H. & C., 
A. kansana Britt.) is so closely related to Artemisia ludoviciana that 
it is impossible to draw a dividing line between them, but it may generally 
be distinguished by its smaller size for it scarcely reaches over two feet in 
height, and by the fact that its principal leaves are mostly divided into linear 
elongate or filiform lobes not more than 1 mm wide. All leaves are white- 
tomentose on both sides. It occurs from Kansas to western Texas and 
Chihuahua westward to Arizona and Utah and is particularly common in 
the arid portions of the southern Rocky Mountains. It is regarded as an 
important cause of hayfever in Utah (ANDERSON 1930). 

Biennial wormwood or sagewort (Artemisia biennis Willd.) is an annual 
or biennial herb with a deep tap root and erect leafy steam, 1 to 3j4 feet 
high, arising from a rosette of crowded leaves which are smooth and twice 
pinnately divided into lanceolate lobes. The stem is also smooth, but striate 
and often tinged with red, ending in a compound leafy spike of small flower 
heads. This species is closely related and similar to A. annua, distinguished 
chiefly by its slightly larger flower heads which are borne more or less erect 
in axillary spikes. It is widely distributed in North America, except in the 
southeast, but, according to HALL and CLEMENTS (1923), presumably na- 
tive from the northern Rocky Mountain states to British Columbia. It is 
typically ruderal, growing occasionally in grass lands, but more generally 

Roger P. Wodehouse .158 Hayfever Plants 

along roadsides and in waste places usually associated with other weeds. It 
is particularly abundant in the Mississippi valley from about the middle of 
Missouri northward. It flowers from August to December, producing large 
quantities of pollen which is the cause of much hayfever. 

Annual wormwood or sagewort (Artemisia annna L.) is a tall annual 
with smooth stems and leaves, nearly inodorous, 1 to 3^/2 feet high, similar 
in habit and appearance to the preceding species to which it is closely 
related. But it may be distinguished by its smaller flower heads which are 
often nodding and borne in a wider and looser terminal panicle of lax 
racemes. It is native of Asia and eastern Europe but now naturalized 
throughout the eastern and central part of the United States as a weed in 
waste places and fallow fields. It flowers in summer but is nowhere abun- 
dant enough to be seriously regarded as a cause of hayfever. 

Dwarf or flat sagebrush (Artemisia Bigelovii Gray) is a dwarf shrub 
with sprawling branches, closely resembling the low forms of A. tridentata. It 
has silvery-canescent leaves, oblong and three-toothed at the ends as in the 
common sagebrush, but their odor is faint and pleasant, but the two species 
are not regarded as closely related in spite of their outward similarity. 

The dwarf sagebrush is common in the southern Rocky Mountains from 
southern Colorado and southern Utah to southwestern Texas and western 
Arizona. In the mixed prairie of northern New Mexico and Arizona it 
often forms a dominant society, also on rocky ridges especially in the cedar 
savannah, but it has a tendency to be replaced by the various grasses with 
which it is associated unless these are removed by grazing. It flowers in 
August and September, but is probably not more than a minor contributor 
to hayfever. 

Common wormwood, sagewort or absinth sage (Artemisia Absinthium 
L.) is a tall spreading perennial herb with silvery, fragrant leaves, reaching 
a height of 6 feet. It is native of Europe but thoroughly established as a 
wayside plant throughout much of the northeastern United States and 
Canada and to a lesser extent westward. Flowering in August and Septem- 
ber, it sheds only moderate amounts of pollen and the plants appear to be 
nowhere abundant enough at present to be more than a local and minor fac- 
tor in hayfever, but they are spreading rapidly. 

Pasture sage, prairie sage, carpet sage or estafiata (Artemisia frigida 
Willd.) is a low perennial herb generally woody at the base and with de- 
cumbent stems forming dense mats, with ascending annual stems seldom 
more than a foot high, with silvery leaves several times dissected into linear 
divisions. It is one of the most characteristic plant societies forming dense 
mats throughout most of the Great Plains and Rocky Mountain regions 
from Alaska to Texas. It flowers from July to October causing much hay- 
fever, and appears to be increasing in importance. Of it HALL and CLEMENTS 
(1923) say : "Its abundance in the climax is partly the result of grazing, and 
is due to the position of the leaves in a mat. As a result it is one of the 
chief indicators of overgrazing on the Great Plains'*. Like A. campestris 
with which it is frequently associated, it is favored by disturbed soils. 

Chapter III __159_ Angiosperms 

Dragon sagewort or linear-leaved wormwood (Artemisia dracunculoides 
Pursh., Artemisia Dracunculus glauca H. & C), also called Indian hair 
tonic and green sagebrush, smooth sagewort, tarragon, estragon, is a 
perennial herb with thick more or less woody rootstock, with erect stems, 
2 to 4*/2 feet high. Its leaves and stems are nearly smooth and tinged with 
red, and not aromatic. It is found almost throughout the United States 
west of the Mississippi River where it is frequently common on the plains 
and mountain slopes. It flowers from July to November, and is regarded 
as a cause of hayfever in California (RowE 1928). Of it HALL and 
CLEMENTS (1923) say: "The pollen . . . sometimes causes severe cases of 
hayfever in Western North America, its importance not so great as that of 
certain other species, such as vulgaris and tridcntata, chiefly because it sel- 
dom occurs in quantity near cities". 

The Gampestris Group : The following four species are so similar 
and closely related that HALL and CLEMENTS regard them as merely 
varieties of the field sagewort, Artemisia campestris L. They are biennial 
or perennial herbs, typically rosette formers, % to 2 feet high, scarcely 
odorous, their stems striate and nearly or quite smooth, ascending, often 
from a decumbent base, frequently tinged with red, their principal leaves 
variously divided into linear or almost filiform divisions rarely more than 
1 mm wide, which are smooth or only slightly silky. The inflorescence is 
an elongate panicle with spike-like branches which are leafy below. The 
heads are small bearing from 5 to 20 marginal flowers which are pistillate, 
and 6 to 30 disk flowers which are staminate. 

The members of the group are found on plains and in the mountains 
almost throughout North America, except in the desert regions. Though 
the various forms are often strikingly dissimilar in appearance, they are all 
alike in essential characters, and it is highly improbable that significant 
allergenic difference exist between them. Of the many different forms 
which have been segregated HALL and CLEMENTS recognize six which are 
worthy of subspecific designation. The following four are of particular 
interest to students of hayfever. 

Field sagewort (Artemisia camporum Rydb., Artemisia pacifica Nutt., 
A. campestris pacifica H. & C.) is a perennial herb, lj/2 to 2 feet high, 
erect from a spreading base, its principal leaves twice divided into narrowly 
linear divisions which are canescent or silky. It is the common form in the 
West, South Dakota and western Nebraska to New Mexico, Arizona, Ore- 
gon, Yukon and Saskatchewan. Flowering in late summer and fall it is an 
important cause of hayfever especially in the Rocky Mountain states. Of it 
HALL and CLEMENTS (1923) say: "It is one of the most unpalatable of 
artemisias to stock and hence is excelled only by A. frigida as an indicator 
of overgrazing. The pioneering quality of the species is also shown in [its] 
frequent occurrence .... in disturbed soils, especially sands and gravels". 

Tall wormwood (Artemisia caudata Michx., Artemisia campestris can- 
data H. & C., fig. 72) is a biennial herb usually with a single stem arising 
from a rosette of leaves which are twice or thrice pinnately cleft into filiform 

Roger P. Wodehouse 


Hayfever Plants 

or very narrow linear divisions. It flowers in August, shedding unusually 
large amounts of pollen which is undoubtedly a serious cause of hayfever 
where the plants are abundant. It is widely distributed principally on 
sandy shores and dunes or occasionally in waste places, most commonly 
in the eastern and central states. ELLIS and ROSENDAHL (1932) state that 
it is the commonest artemisia of the Upper Mississippi valley. It is fairly 
common throughout North and South Dakota and abundant in most parts 
of Minnesota except the northeastern corner, and is common around Min- 
neapolis and St. Paul and on vacant lots within the cities. 

FIG. 72. Tall wormwood (Artemisia campcstris caudata). 

Canadian mugwort (Artemisia canadensis Michx., A. borealis Pallas, A. cam- 
pestris borealis H. & C.) is the northern form of the campestris group, ranging from 
Greenland and Hudson Bay to Vermont, western Ontario, Colorado and Washington. 
It flowers from July to August, but is of little consequence in hayfever. 

Seashore mugwort (Artemisia pycnocephala DC., A. campestris pycnocephala 
H. & C.) is a small perennial herb not more than 2 feet high, with several or many 
erect stems arising from a small basal rosette of densely silky villous leaves. It is 
restricted to sandy beaches along the Pacific ocean from Oregon south to Point Sur, 
California. It flowers during summer and fall, but sheds relatively little pollen and is 
nowhere abundant. It is regarded as important in parts of California (RowE 1928). 

Chapter III 161 Angiosperms 

Silvery wormwood (Artemisia filifolia Torn), also called sand sagebrush, is a 
rounded or straggling shrub reaching about 4 feet in height with mildly and pleasantly 
scented leaves which are ternately parted into filiform divisions or entire and filiform, 
often with smaller fascicled leaves in their axils. It is found often dominant in sandy 
soils from Nebraska and Wyoming to Nevada, Chihuahua and Texas and is perhaps 
the most widespread shrub on inland dunes and sand hills from Nebraska to Arizona. 
It is an important cause of hayfever during the latter part of summer. 

Budbrush, budsage or spiny sagebrush (Artemisia spinescens D. C. Eat., Picro- 
thamnus desertorum Nutt.) is a low spiny villous shrub scarcely reaching 1 foot in 
height, with leaves pedately divided and secondarily lobed with narrow divisions, with 
few flower heads which are solitary or arranged in small racemes in the axils or at 
the ends of short branches. Its achenes are ellipsoidal and densely arachnoid hairy. 
In its spinescent character and densely hairy flowers it differs from all other members 
of the genus, and this is regarded by RYDBERG and other authors as sufficient ground 
for separating the species from the artemisias and placing it in the monotypic genus 
Picrothamnus Nutt., but HALL and CLEMENTS regard these characters as relatively 
unimportant, developed in response to the unfavorable environment which it generally 
occupies. It is a shrubby dwarf rosette former of dry saline or alkaline soils. It is 
common on arid planes and slopes from Montana and Colorado to New Mexico, east- 
ern California, eastern Oregon and Idaho. It flowers from March to June and is un- 
doubtedly an important cause of hayfever. 

Common sagebrush or mountain sagebrush (Artetnesia tridentata Nutt.) 
sometimes erroneously called "black sage" is typically a shrub 3 to 12 feet 
high, but may be dwarfed by grazing or reach almost tree size under favor- 
able conditions. It has a strong aromatic pungent odor. The main stem is 
usually trunk-like with dark shreddy fibrous bark, but the twigs are gray 
or white with a fine tomentum, ending in dense leafy panicles of numerous 
small heads of flowers which shed enormous quantities of pollen from July 
to late September. 

The common sagebrush is the most abundant and important of all the 
artemisias as a cause of hayfever, in many places greatly outranking the 
ragweeds. HALL and CLEMENTS (1923) state that it is "the most common 
and widely distributed shrub of western North America especially on arid 
plains of the Great Basin, but ranging to timber line in the mountains ; 
central Montana to North Dakota, eastern Colorado, New Mexico, Lower 
California, and eastern British Columbia". Throughout this wide area 
covering a variety of habitats, it occurs in a number of fairly well marked 
varieties some half dozen of which have received specific names. For- 
tunately, however, these have not yet found their way into hayfever litera- 
ture. It is to be hoped that they will continue to be ignored for no possible 
advantage could be gained by their recognition. The species ranges in size 
from a dwarf similar in appearance to A. Bigelovii, usually the result of 
overgrazing, to a small tree 20 feet high. It forms the bulk of the vegeta- 
tion of the Great Basin and ranges into the mixed prairie and bunch-grass 
prairie, especially where overgrazing has given it an adventage in com- 
petition with the grasses. This is especially true in eastern Oregon, north- 
eastern California, and southern Idaho where the original grass land has 
been almost completely replaced by sagebrush. It is eaten by grazing 
animals only when nothing else is available, but because it can be used to 
carry stock through the winter it is not regarded with disfavor. So if 

Roger P. Wodehouse 162 Hay fever Plants 

current grazing practices are allowed to continue, sagebrush promises to 
become an even more serious cause of hayfever than it already is. 

Senecioneae: The groundsel tribe is a large group, next to the 
Aster eae the largest in the family, comprising more than 1400 species, but 
about 1200 of these belong to the genus of groundsels (Senecio), the largest 
genus of the family. Apparently all are insect pollinated and of no conse- 
quence in hayfever. 

Gynareae : The thistle tribe includes such familiar forms as the 
thistles (Cirsiunij Carduus, Cnicus), the burdocks (Afctium), the globe 
thistles (Echinops), the star thistles (Centaurea) and the globe artichoke 
(Cynara Scolymus L.). They are distinguished by having only perfect and 
tubular flowers with corollas deeply five-cleft. They are insect pollinated 
and exceptionally well adapted to this mode of pollination so that it is 
unlikely that their pollen could ordinarily cause hayfever, though some of 
the thistles, especially the bull thistle (Cirsium lanceolatum Hill) and the 
Canada thistle (C. arvensc Scop.) have been suspected of doing so. 

The pollen-grain forms of this tribe are exceedingly various in all their 
characters. They are mostly large, generally over 40/u, in diameter, in the 
globe thistle (Echinops sphaeroccphalus L.) reaching 70/A in length. Gen- 
erally the exine is very thick and coarsely granular. The furrows are 
extremely various but are usually short or of medium length, occasionally 
so short as to coincide in extent with the enclosed germ pore (e.g., some 
species of star thistle). Occasionally the furrows are long and tapering 
as in the grains of burdock (Arctiwn Lappa L.). The spines when present 
tend to be broadly conical, but in the grains of many species they are repre- 
sented by the merest vestiges (the globe thistle, some species of star thistle 
and blessed thistle Cnicus benedictus L.), or entirely absent (some species 
of star thistle). 

Mutisieae: The mutisia tribe is almost entirely South American and 
South African, though represented in the West Indies by a few shrubby and 
herbaceous forms, and in the southern part of the United States by such 
forms as Trixis and Perezia of California, and Chaptalia of Florida and 
the Gulf states. The group is, however, best known in America through 
the Natal or African daisy (Gerbera Jamesoni Bolus) which, though native 
of South Africa, is extensively cultivated and a well known hot-house plant 
with beautiful daisy-like flower heads with long narrow and variously 
colored rays rising on naked stalks from a rosette of broad basal leaves. 
The flower heads of the others are either with or without rays, the corollas 
commonly five toothed and bilabiate or, less frequently merely deeply five 
cleft, suggesting a close relationship with the thistle tribe. 

The pollen grains of the mutisia tribe represent several distinct and 
apparently unrelated forms. This, it appears, is probably because the tribe 
is not a natural group. The grains of most resemble those of the thistle 
tribe, having thick, coarsely granular exine, furrows of medium length, and 
spines, when present, broad and short but the spines are generally repre- 

Chapter III 163 Angiosperms 

sented only by vestiges, reminiscent of the grains of most of the star thistles 
and in one small subtribe, the Nassauvinac, and the South American genus 
Barnadesia they are entirely absent. The grains of the latter are quite 
different from those of all other members of the tribe. They are charac- 
terized by elaborate sculpturing resembling that of the grains of the Cicho- 
rieae except for their lack of spines. There is, however, evidence to show 
that both the Nassauvinac and Barnadesia are not genetically closely related 
to the rest of the tribe nor to each other. This interesting phase of the 
subject has been discussed in greater detail elsewhere (WODEHOUSE 1928c, 
1929a, 19296, 1935). 

Gichorieae: The chicory tribe comprises about 70 genera and 1500 
species, mostly herbs with milky juice. They differ from all other members 
of the family in having all flowers of the heads perfect and with strap- 
shaped corollas generally five-toothed at the apex. This is the most distinct 
and sharply separated tribe of the family and, as has already been pointed 
out, is regarded by some botanists as a separate family (Cichoriaceae Brit- 
ton and Brown) or as a subfamily or series, Liguliflorae Gray. Never- 
theless there is no doubt that the group belongs to the Composite family and 
it is generally believed to be rather closely related to the two preceding 

The Cichoricae are well known to us through such familiar and useful 
species as the common chicory (Cichorium Intybus L.), endive (C. Endivia 
L.), lettuce (Lactuca sativa L.), oyster plant or salsify (Tragopogon por- 
rifolins L.), black salsify (Scorzoncra hispanica L.), and the Spanish oyster 
plant (Scolymus hispanicus L.). All are strictly insect pollinated, and 
though several species are common and troublesome weeds, only one, the 
common dandelion (Taraxacum offidnalc Weber), has ever been suspected 
of causing hayfever. The dandelion is said to be an important contributor 
to early summer hayfever in the Pacific Northwest (STIER, HOLLISTER and 
BONSER 1930) and in Utah (ANDERSON 1930, BARRETT 1934). 

The pollen grains (fig. 58B) of the Cichorieae are widely divergent 
from the basic form of the family. They have the three characteristic 
furrows and pores, but with few exceptions are distinctive in having an 
elaborate and beautiful system of sculpturing. Their exine is thrown into 
high vertical spine-topped ridges which divide the surface of the grain into 
angular lacunae. The number and arrangement of these is various in the 
different species but they are nearly always arranged in symmetrical pat- 
terns of striking beauty. In this respect they resemble the grains of the 
ironweed tribe but may be distinguished by their simple patterns, composed 
of 6 to 21 lacunae as compared with 30 or more in the grains of the iron- 
weeds. These beautiful grains have been made the subject of an extensive 
study by the author and reported elsewhere (WODEHOUSE 1935). 

Chapter IV 

In recent years as the necessity for a knowledge of the local hayfever 
flora is becoming more generally understood among students of hayfever 
more and more regional surveys are being reported. A search of the medi- 
cal literature to date has brought to light about 135 reports of regional sur- 
veys which seemed worthy of consideration. All but a few states are repre- 
sented by at least one report, some by many. As would be expected these are 
not at all evenly distributed over the country, but tend rather to follow the 
concentrations of population, coming in greatest frequency from the states 
on or near the Atlantic seaboard, and next from those of the Pacific, with 
the central part of the country, except for the Great Lakes region, and 
Colorado and Utah, very poorly represented. The reports vary in com- 
prehensiveness from a casual observation of a plant or two, to careful and 
painstaking studies often conducted over several years, and in scope from 
those covering a single community or town to those covering whole states 
or groups of states. 

The present chapter is largely a compilation of these reports. For 
convenience of presentation the country is divided into ten sections as 
indicated on the accompanying map. These divisions are arbitrarily chosen ; 
their size and arrangement is entirely a matter of convenience in presenting 
the data. 

Most of the published reports of surveys include many species which 
are of little consequence in hayfever, or none whatever. As far as possible 
I have tried to eliminate these, and still include in the tables all those which 
appear to be important enough to merit consideration in the diagnosis and 
treatment of hayfever occurring in the region represented. Those which 
are of primary importance are printed in bold face type. 

The flowering periods recorded in the tables are for the most part com- 
posites of a number of reports, generally varying somewhat. Each week of 
the flowering span of a species is represented by a vertical stroke, the dark 
strokes representing general flowering, the light strokes representing local 
or less general flowering. 

I. The Northeastern States (New England States, New York, 
New Jersey and Pennsylvania) : 

Hayfever in this region falls into three well marked seasons: the 
early-spring or tree season which starts with the first appearance of 
spring, generally early in April, and extends well into May ; the late spring 
or early-summer season, which is also called the grass or grass-plantain 
season, starting about the middle of May and lasting until the middle of 
July ; and the late-summer or ragweed season which starts very definitely 
at about the middle of August, in some places always exactly on the 15th, 
and generally fades out toward the end of September, not on account of 

Roger P. Wodehouse 


Hayfever Plants 

frost as generally stated, but with the normal going-to-seed of the late- 
summer vegetation. 

Early Spring Hayfever: Of these three seasons the first, or tree 
hayfever season, is the least important in spite of the fact that during this 
time the pollen in the air reaches its maximum concentration ; the pollen of 
oak alone occurs in much greater abundance than that of ragweed in the 
later season, and the pollen of the birches is almost its equal, yet relatively 
few cases of hayfever from these or other tree sources are recorded. But 
those which do occur may be very severe, and generally several species are 
involved (Turx and BLUMSTEIN 1937). 

(New England States, New York, New Jersey and Pennsylvania) 

Ulmus* (Elms) 

Acer* (Maples) 

Salix* (Willows) 

Populus* (Poplars) 

Betula* (Birches) 

Quercus* (Oaks) 

Fagus (Beeches) 

Fraxinus americana (White ash) 

Alopecurus pratensis* (Meadow foxtail) 
Anthoxanth. odorat. (Sw. vernalgrass) 
Plantago lanceolata* (English plantain). 

Poa pratensis (June grass) 

Dactylis glomerata (Orchard grass) 

Rumex Acetosella (Sorrel dock) 

Festuca rubra (Red fescue) 

Festuca elatior (Meadow fescue) 

Poa compressa (Canada bluegrass) 

Phleum pratense (Timothy) 

Agrostis alba (Redtop) 

Iva oraria* (Marshelder) 

Solidago* (Goldenrods) 

Ambrosia elatior (Short ragweed) 

Ambrosia trifida (Tall ragweed) 

Xanthium (Cockleburs) 






* Discussed in the paragraphs immediately following. 

Elms. The commonest elm is the white (Ulmus americana), preva- 
lent throughout the region. Also fairly common is the slippery elm 
(U. julva) and in the New England States, particularly in the region of 
Boston, is the European elm (17. campestris), formerly commonly planted 
along city streets and in parks. 

Willows. Many species of willow occur in the region. The com- 
monest are the European purple osier, pussy willow (Salix discolor), 
black, crack and weeping willows. 

Maples. The commonest are silver, red, sugar, Norway and sycamore 
maples, and box elder. The latter sheds much more pollen than the others 
but is rather localized in distribution, and seldom common. 

Chapter IV 167 Regional Surveys 

Poplars. Many species of poplar occur. The commonest are the 
European white and black poplars, large-toothed and trembling aspens, the 
necklace poplar, tacamahac and Carolina poplars. They all flower at about 
the same time. 

Birches. The three commonest species of birch are the gray (Betula 
populifolia) , yellow and black, flowering in succession and with their periods 
overlapping. The paper birch occurs naturally in the northern part of 
New England and Pennsylvania, and it and the European white birch are 
frequently planted in city parks and streets. The birches rank perhaps 
second to the oaks in importance, and the cases of hayfever from their pollen 
which have been recorded appear to be very severe. 

Oaks. Many species of oak occur in this region ; the commonest are 
black (Quercus vclutina), Spanish, white, chestnut, swamp-white and shrub 
oak (Q. ilicifolia). They all flower at about the same time and it is to their 
combined efforts that is due the enormous pollen count that is recorded 
during about the two weeks in the middle of May. Oak is probably the 
most important tree pollen in the region. Nevertheless not very many 
cases are recorded even from it, but those which do occur are often severe. 

Often included in pollen lists for this region are sweet gum and eastern 
sycamore, but neither of them appears to be of importance in hayfever. 

Early Summer Hayfever: The second or grass-plantain season is 
very much more important than the first season. It starts early in May 
when sweet vernalgrass begins to flower. This is quickly followed by June 
grass, orchard grass, timothy and redtop, flowering more or less in succes- 
sion. These five species appear to be responsible for nearly all the grass 
hayfever. There are, however, a number of other grasses which are of some 
importance locally. For example, red fescue, meadow fescue and wild oat- 
grass (Danthonia spicata) are heavy pollen shedders but seldom abundant 
enough to be very important. Quack grass (Agropyron re pens) is only a 
meagre pollen shedder. Meadow foxtail (Alopecurus pratensis) is locally 
abundant particularly in the New England States. It is a heavy pollen 
shedder similar to timothy and may occasionally be a local factor of impor- 
tance. Canada bluegrass is said to be important in parts of Pennsylvania 
( SCOTT, CRIEP and GREEN 1936) and eastern Massachusetts (RACKEMANN 
and SMITH 1931&), but though it occurs elsewhere it is not common enough 
to be of much importance. 

There are several species of plantain distributed abundantly throughout 
the region, but of these only the English plantain is a factor in hayfever. 

Late Summer Hayfever: The third, the ragweed, season is by far 
the most important, accounting for many more cases of hayfever than the 
other two together. The hayfever of this season is due practically entirely 
to the pollen of the short and tall ragweeds. In the New England States 
and Maritime Provinces it is almost entirely the short ragweed, the tall 
ragweed being either entirely absent or occurring only sparingly. In the 
southern and western part of the region, however, the tall ragweed is fully 
as abundant as the short, and often much more so. 

Roger P. Wodehouse 168 Hayfever Plants 

Several species of cocklebur are found scattered along railroad embank- 
ments, roadsides, river courses, etc., but they are never very abundant and 
the records of the pollen slides show that their pollen is not an important 
factor. There are many species of goldenrod growing profusely throughout 
the area but most of them shed too little pollen to merit consideration, and 
not until the showy goldenrod (Solidago speciosa) comes into flower in 
September does goldenrod pollen appear on the slides, then for a short 
period it may even outrank cocklebur pollen. 

Marshelder (Iva or aria) grows in great abundance in the tidal marshes 
along the coast and appears to be occasionally a local cause of hayfever. 

Pigweed, Mexican tea and lambsquarters grow abundantly throughout 
the region and their pollen may be detected in small amounts in the air 
during most of the summer, but there is no evidence to suggest that they 
are of any importance in hayfever. 

Marsh grass (Spartina patens) is extremely common in tidal marshes 
all along the coast and may be a local contributor to midsummer hayfever. 
RACKEMANN and SMITH (1931&) include it in their list of hayfever plants 
of eastern Massachusetts, and it appears to be a contributor to late-summer 
hayfever on parts of Long Island. 


The earliest report is that of WALKER (1921). He reports 12 cases sensitive to 
pollen of trees, including one each to that of oak, maple and willow, all of which 
were benefited by treatment with extracts of the corresponding pollen; and one each 
to the pollen of pine, poplar and ash, which were not treated. VANDER VEER, COOKE and 
SPAIN (1927) with the help of Professor HODGSON of Montclair, N. J., made an 
exhaustive study, presumably applicable to the entire area of the northeastern states, 
and constructed a useful pollen calendar, showing the flowering periods of 50 or more 
plants common in this area which present hayfever possibilities. This report also 
gives the different kinds of pollen which were used in treating a random group of hay- 
fever cases. Ragweed tops the list with 696 cases, timothy second with 420 and plantain 
third with 237, but birch, oak and goldenrod were used in only 59, 56 and 14 cases 

RACKEMANN and SMITH (1931a, 1931&) give a useful list of hayfever plants of 
New England with their dates of flowering, and state that meadow fescue, meadow 
foxtail, lambsquarters, artemisias, cocklebur and tall ragweed, while occurring in New 
England, are not found in stands large enough to be significant. WILMER and COBE 
(1932) exposed oiled slides in Philadelphia, Pa., and showed that the fluctuations in the 
pollen count corresponded to symptoms of hayfever. 

The present author (WODEHOUSE 1933) reported in the form of a graph a record 
of all the different kinds of pollen caught on atmospheric pollen slides coated with 
glycerine jelly throughout one entire hayfever season in Yonkers, N. Y. More than 
35 different kinds were identified and their dates of appearance and relative abundance 
recorded. These showed that the pollen of the oaks greatly outranked that of the 
ragweeds and that of birch approximately equalled it, and that during the month of 
May the combined count of all atmospheric pollen is very much higher than at any 
other time. 

FREUD (1935) published a list of anemophilous plants with hayfever possibilities 
of the Capitol District, New York. SCOTT, CRIEP and GREEN (1936) reported atmos- 
pheric pollen counts of the grasses, chenopods and ragweeds for the region of Pitts- 
burgh, Pa., including Canada bluegrass among those of first importance. THOMMEN 
(1930) discussed the importance of spring hayfever in the northeastern states, includ- 
ing a table of the pollination periods of the most important trees causing hayfever in 
the section east of the Mississippi River and north of Tennessee and North Carolina. 

Chapter IV 169 Regional Surveys 

report mold and pollen surveys of southeastern New England. Grass and weed pollen 
they find to be more abundant in the suburbs than in the cities, and Alternaria spores 
are most abundant during the ragweed season. 

Several of the standard textbooks devote a few pages to the botanical aspects of 
this region; VAUGHAN (1931) gives a list of "The more common plants of New Eng- 
land producing light dry pollen" compiled by Professor M. L. FERNALD of Harvard 
University, and reported by RACKEMANN (1931). THOMMEN (1931) lists with their 
flowering periods, the trees, grasses and weeds which are believed to be the most 
important causes of hayfever in the vicinity of New York City. HANSEL (1936) gives 
a brief summary of the literature dealing with the New England States and New York. 
RACKEMANN (1931) gives a brief summary of some of the regional surveys, including 
FERNALD'S original list of plants with hayfever possibilities and their times of flowering 
in the New England States. 

Hayfever Resorts: Few places in this region are entirely free from ragweed 
pollen. In New York State much of the Adirondack Mountain region is nearly free 
from ragweed pollen, particularly Hamilton and Franklin counties, owing to the fact 
that these regions are still heavily wooded. The New York State Department of 
Health (Anonymous 1943) has fully recognized the value of these places as hayfever 
resorts and is taking determined steps to keep them free. From the Department 
may be obtained without charge detailed information and maps of the free areas. 

Great South Beach on Long Island is variously reported. It is a long sandy strip 
lying off the south shore of the Island with Great South Bay between. There is only 
an insignificant amount of ragweed growing on the Beach so that the patient's chances 
of freedom from hayfever depend upon the unpredictable direction of the wind. A 
land breeze brings little or no relief but a sea breeze brings nearly complete freedom 
from pollen. The region of Montauk Point at the extreme eastern end of Long Island 
is somewhat better situated and can be counted on as nearly free from ragweed pollen. 

Large sections of Maine which still remain heavily forested are comparatively 
free from ragweed pollen. SYLVESTER and DURHAM (1938) and SYLVESTER (1939o) 
report a study of the hayfever situation in Maine. Throughout most of the state the 
hayfever season is short and the load of atmospheric pollen light ; Portland has 18 days 
of hayfever but the northern section of the state (Aroostook County) is nearly free. 
Elsewhere in the state the region of Rangeley Lake, Machias and Greenville experience 
not more than three days each season of pollen sufficiently heavy to cause hayfever. 

The White Mountains in New Hampshire have long been famed for their freedom 
from hayfever. The principal resort is Bethlehem. It owes its advantage to its eleva- 
tion and short growing season which prevent the growth of ragweed plants, and to 
the fact that much of the surrounding territory from which pollen might be blown, is 
still heavily forested. 

Much of Nova Scotia is free from ragweed pollen, particularly the parts which 
still remain heavily timbered. But the famed Annapolis Valley has an abundance of 
ragweed from which many cases of hayfever are recorded. 

II. The Middle Atlantic States (Delaware, Maryland and District 
of Columbia) : 

Early Spring: Hayfever of this region falls into the same seasons as 
in the New England States. The early spring or tree hayfever season 
accounts for about 4.4 per cent of the cases (BERNTON 1923). It starts 
early in March with the maples and elms, followed by several species of 
poplar and ash, but these are all of relatively little importance. The oaks 
which flower a little later are by far the most important of the trees. Ac- 
cording to BROWN (1932), "There are at least 20 different species growing 
in the Middle Atlantic States", the principal species being the black (Quer- 

Roger P. Wodehouse 


Hayfever Plants 

cus velutina), white and red oaks. All species flower at about the same 
time and account for about 45 per cent of the tree cases (BERNTON 1930). 
Next in importance among the trees are the eastern sycamore and hickories, 
each accounting for about 13.7 per cent of the tree cases. Four species of 
hickory, Carya cordiformis, C. alba, C. ovata and C. glabra, are common in 
the region, but they are not generally distinguished from each other in hay- 
fever studies. Of peculiar interest in this region is the paper mulberry 
(Broussonetia papyrifera). Though it accounts for relatively few cases 

(Delaware, Maryland and District of Columbia) 


















Acer (Maples) 


Acer Negundo (Boxelder) 


Acer platanoides (Norway maple) 
Ulmus (Elms) . . . 




Populus deltoides (Necklace poplar) 
Fraxinus americana (White ash) 



Betula alba (White birch) 



Betula nigra (Red birch) 


Salix (Willows) 


Quercus* (Oaks) 



Carya (Hickories) 


Fagus grandifolia (American beech) 
Platanus occidentalis (Sycamore) 
Juglans nigra (Black walnut) 



Juglans cinerea (Butternut) 
Broussonet. papyrif. (Paper mulberry) 
Anthoxanth. odorat. (Sw. vernalgrass) 
Plantago lanceolata* (English plantain) 
Rumex Acetosella (Sorrel dock) 
Dactylis glomerata (Orchard grass) . . . 
Poa pratensis (June grass) 












Festuca elatior (Meadow fescue) 
Lolium perenne (Perennial ryegrass).. 
Agrostis alba (Redtop) 





Phleum (Timothy) 



Cynodon Dactylon* (Bermuda grass)... 





Ambrosia trifida (Tall ragweed) . 


Ambrosia elatior (Short ragweed) 
Xanthium (Cockleburs) 




* Discussed in the accompanying paragraphs. 

(5.8 per cent of the tree cases) these may be very severe and are likewise 
sensitive to pollen of the related mulberries and Osage orange (Madura 
pomifera) which also grow in this region (BERNTON 1928). Next in im- 
portance are the birches ; several species occur but the principal one is the 
red or river birch. The poplars are relatively unimportant ; though the 
trees are abundant they are principally Carolina poplar which sheds but 
little pollen. 

Late Spring : Among the causes of hayf ever during the late spring 
or early summer season, orchard grass is the most important (AQUARONE 

Chapter IV 171 Regional Surveys 

and GAY 1931), greatly outranking timothy. Indeed the latter is found 
to be of little importance in Baltimore. Other grasses which contribute to 
the hayfever of this season are much the same as those recorded for the 
New England States, except that Dallis grass, Bermuda grass and other 
southern species are reported to occur in this region, but they appear to be 
of little consequence. 

Plantain. BERNTON (1925) finds that in this region plantain pollen 
accounted for 4.3 per cent of a series of hayfever cases, and AQUARONE and 
GAY (1931) have designated this period the plantain season, since its flower- 
ing period bridges the gap between the early and late summer hayfever 
seasons, extending from July 1 to August 15. 

Late Summer: Hayfever in the late-summer season appears to be 
due almost entirely to the pollen of the short and tall ragweeds, contributed 
to slightly by cocklebur, and locally by marshelder. 


The earliest record is that of BERNTON (1923) in which is published a list with 
dates of flowering of all plants with hayfever possibilities of the Baltimore region. 
The same author discovered the importance of plantain (BERNTON 1925) and paper 
mulberry (BERNTON 1928). 

Similar work was done by BROWN (1927) for the District of Columbia, dealing 
only with the late-spring or early-summer season. He showed that 12 out of 13 
of the cases suffering from hayfever at this time were sensitive to the pollen of 
sweet vernalgrass, June grass, orchard grass, timothy and redtop, and about one sixth 
were sensitive to the pollen of plantain. In a later paper BROWN (1932) extended 
his observations to include the whole of the Middle Atlantic States and all seasons. 
He states that the early-spring season accounts for 4 per cent, early-summer 32 per 
cent, and late-summer 64 per cent of the hayfever cases. Among the trees he states 
that the oaks are the most important, sycamore next, and "The hickories of which 
there are at least seven different species in the Middle Atlantic States are responsible 
for quite a few cases". 

AQUARONE and GAY (1931) made a pollen survey of Baltimore exposing at the 
same time oiled pollen slides. Their report presents a list of plants which cause hay- 
fever, and others of which the pollen becomes atmospheric, together with their dates 
of flowering. Pollen counts are reported as graphs showing the record of grass, plan- 
tain and ragweed. The peak of the grass curve, about 400 grains per square centimeter 
of slide surface, occurred about the first of June and is accounted for by orchard grass. 
"Plantago lanceolata pollen appeared at a surprisingly constant rate of about 25 grains 
per square centimeter daily from mid-May to early August." The ragweed curve 
showed two major peaks, August 28 and September 19, reaching about 160 and 180 
grains per square centimeter respectively. This work was extended by PATTERSON and 
GAY (1932), giving a useful schematic chart of the pollination periods of the different 
trees, grasses and weeds of Baltimore, and curves for pollen counts of pine, oak-beech, 
plantain, grass, mold spores and ragweed. Oak-beech pollen reached its peak of 351 
grains per square centimeter on May 5, pine 104 on May 2, hickory 47 on May 1. 
Plantain reached a peak of only 21 grains on June 15 while grass pollen scarcely reached 

Several of the standard textbooks devote a few pages to the hayfever of this re- 
gion. HANSEL (1936) and VAUGHAN (1939) give brief reviews of the literature sum- 
marizing the results of all the important contributions to our knowledge of the hayfever 
of this region. VAUGHAN (1931) reprints the more important tables from BERNTON'S 

Roger P. Wodehouse 


Hayfever Plants 

III. The Virginias and Carolines (Virginia, West Virginia and 
North and South Carolina) : 

The Maples. Several species of maple are represented and appear to 
be rather important. Silver, red, sugar and Norway maples are common 

(Virginia, West Virginia and North and South Carolina) 

Acer* (Maples) | 

Acer saccharum (Sugar maple) 

Acer Negundo (Boxelder) 

Ulmus* (Elms) | 

Juniperus virginiana* (Red cedar) 

Salix (Willows) 

Corylus (Hazel) 

Betula lutea (Yellow birch) 

Betula lenta (Black birch) 

Betula nigra (Red birch) 

Quercus* (Oaks) 

Taxodium distichum (Cypress) 

Juglans cinerea (Butternut) 

Juglans nigra (Black walnut) 

Populus (Poplars, cotton wood) 

Platanus occidentalis (Sycamore) 

Fagus grandifolia (American beech) .... 

Morus (Mulberries) 

Celtis occidentalis (Hackberry) 

Fraxinus americana (White ash) 

Fraxinus pubescens (Red ash) 

Liquidambar Styraciflua (Sweet gum).. 

Carya Pecan (Pecan) 

Carya* (Hickories) 

Broussonet. papyrif. (Paper mulberry). . 

Poa annua (Annual bluegrass) 

Lolium perenne (Perennial ryegrass) 

Rumex Acetosella (Sorrel dock) 

Plantago lanceolata (English plantain) 
Anthoxanth. odorat. (Sw. vernalgrass) . 

Dactylis glomerata (Orchard grass) 

Holcus lanatus (Velvet grass) 

Poa pratensis (June grass) 

Poa trivialis (Rough meadowgrass) 
Chenopodium album (Lambsquarters) . . 
Amaranthus spinosus (Spiny amaranth) 

Amaranthus retroflexus (Pigweed) 

Festuca rubra (Red fescue) 

Festuca elatior (Meadow fescue) 

Phleum prat en se (Timothy) 

Agrostis alba (Redtop) 

Cynodon Dactylon* (Bermuda grass) 

Sorghum halepense (Johnson grass) 

Paspalum dilitatum (Dallis grass) 

Iva frutescens (Marshelder) 

Cyclachaena xanthifolia (Burweed) 

Ambrosia bidentata (Southern ragweed) 

Ambrosia trifida (Tall ragweed) 

Ambrosia elatior (Short ragweed) 

Xanthium (Cockleburs) 







* Discussed in the accompanying paragraphs. 

and flower very early, but perhaps even more important is the boxelder 
(Acer Negundo) since it is entirely wind pollinated and rather common. 

Chapter IV 173 Regional Surveys 

The different species flower more or less in succession and show a wide 
range in their flowering periods depending on weather conditions, hence 
the long flowering period shown in the table. VAUGHAN, GRAHAM and 
CROCKETT (1933) record silver maple and red maple flowering in January. 

Elms. Three species of elm are common to the region, the winged, 
white and cork elms, the former which is frequently planted as a street 
tree, preceding in its flowering the two latter by several weeks. It is 
recorded as early as January (VAUGHAN, GRAHAM and CROCKETT 1933). 

Junipers. Both the red cedar (Juniper us virginiana) and the com- 
mon juniper (/. communis) are common in the region. They usually 
flower in April but are recorded as early as February. 

Hickories. The hickories, including pecan, appear to rank rather high 
as causes of hayfever but the various species are not usually distinguished 
in hayfever studies. Carya cordijortnis, C. minima, C. ovata, C. alba, C. 
glabra and C. Pecan are recorded for the region. They all flower at about 
the same time, during the last weeks in April and the first in May. 

Oaks. There are many different species, including such as Quercus 
rubra, Q. palustris, Q. nigra, Q. Phellos, Q. alba, Q. virginiana, Q. coccinea 
and others. On account of the wide variation of their flowering periods 
influenced by weather conditions, oak pollen may be found in the air 
throughout April and May and sometimes even longer. 

Poplars. The European white poplar (Populus alba) is reported 
(BLOMQUIST and COSTING 1936) to be fairly common in North Carolina, 
spreading by root suckers and forming thickets about old home sites. The 
necklace poplar (P. balsamifera virginiana Sarg.) is fairly common in moist 
soil along streams and lakes, also some of the cultivated varieties and 

Bermuda grass is important principally in the southern part of the 
region and is abundant in Charleston. 

Several species of mugwort, as Artemisia annua, A. biennis and A. 
frigida are reported to grow in the region but are scarcely abundant enough 
to be important. Russian thistle is also occasionally observed but is not 
regarded as a cause of hayfever. Sorrel dock (Rumex Acetosella) is abun- 
dant and sheds a good deal of pollen which may occasionally be a factor to 
be reckoned with. 


The hayfever problem in Virginia has been thoroughly studied by VAUGHAN and 
his co-workers and the results of their work is admirably reported in their six years' 
survey (VAUGHAN, GRAHAM and CROCKETT 1933) in which they give a list, with their 
flowering periods, of all the plants with hayfever possibilities. They emphasize the 
fact that there is much variation from season to season and in different localities, 
particularly among the trees and to a lesser extent among the grasses. They point 
out, for example, that June grass may be flowering in Richmond as early as January 
15, though it ordinarily does not flower until June. VAUGHAN (1931) gives a complete 
list of 'Airborne Pollen Plants of Southern and Western Virginia' prepared by HORATIO 
S. STAHL, and a list of 'Hayfever Plants in the Vicinity of Richmond, Va.' prepared 
by ANNA CLARK. The first two of these lists state the time of flowering of the various 
species, while the latter states their relative abundance. VAUGHAN in another list in the 
same publication gives the relative frequency of positive sensitizations found to the 

Roger P. Wodehouse 174 Hayfever Plants 

various hayfever species as compared with ragweed in Virginia and the Carolinas. 
Giving short ragweed a rating of 100, the grasses are found to range from 2 to 28, 
hickory 14, plantain 22. 

BLANTON (1932) gives a list of the 'Pollination periods of trees east of Mississippi 
and north of North Carolina', and records of the pollen counts on oiled slides for the 
total amount of pollen. The chief trees in Richmond, he states, are pin oak, maples, 
elms, cottonwoods, ginkgo, mulberries, sycamore, poplars and catalpa. He also states 
that none of his hayfever cases reacted to plantain pollen. 

HOCH and WARING (1933) published a classified list of plants with hayfever possi- 
bilities for Charleston, S. C. and vicinity within a radius of 10 miles, and furnish a key 
which 'may be used as a helpful guide in determining the prevalence ... of the more 
important pollens of this section.' 

TODD (1934) reports his observations on the local flora and the results of daily at- 
mospheric pollen counts in Charlotte, N. C. as recorded on oiled slides, both by the 24 
hour gravity count and the 5 minute blower count devised by DUKE, He reports maple 
and elm flowering January 31, but the grasses, he says, begin to show on the slides 
in definite numbers on April 7, rapidly increasing throughout the month, and he em- 
phasizes the importance of the trees and grasses in this section, especially the grasses 
because their pollen carries on, showing even increased counts during the main part of 
the ragweed season, making it necessary to combine grass and ragweed pollen in 
treating patients for the late-summer hayfever. His figures also show that in 1933 
Charlotte's total pollen count of 1,563 is 2J^ times as high as Charleston's and */$ that 
of Raleigh as reported by O. C. DURHAM, and that Charlotte's daily average ragweed 
count is higher than that of Richmond, Philadelphia and New York. 

COCKE (19386) reports an atmospheric survey of Charlottesville, Virginia for the 
year 1936. He gives a list of the wind pollinated trees, grasses and weeds and the 
record of 46 different kinds of pollen caught on his atmospheric pollen slides. This 
should prove one of the most useful reports for students of hayfever in Albermarle 

These studies show that hayfever in the Virginias and Carolinas, as compared with 
that of more northern sections, is of longer duration, starting earlier and ending later, 
more various from year to year and from place to place, and is practically continuous 
throughout the growing season, not occurring in three well marked seasons as in the 
more northern provinces. Also a large number of species of plants are involved, and 
the trees and grasses assume relatively greater importance. Albeit hayfever here is no 
worse and, as in most places in the East, is mainly caused by the tall and short rag- 

IV. The North-Central States (Ohio, Kentucky, Indiana, Michigan, 
Illinois, Iowa, Eastern Missouri, Wisconsin and Southern Ontario) : 

The flora of the north-central region is in the main, eastern in character, 
and in its principal elements is similar to that of the northeastern states. 
The same three hayfever seasons may be recognized, that of the early 
spring due to the pollen of trees, that of the late spring or early summer, 
due principally to the grasses, and that of the late summer due principally 
to the ragweeds. Of these the earliest season is of relatively little impor- 
tance, even somewhat less than in the Northeast. The second season is 
much more important, but the greater part of the hayfever occurs in the 
late summer season. As in the Northeast, June grass, orchard grass, 
timothy and redtop account for the major portion of early-summer hay- 
fever, and the ragweeds, especially the short, are much the most important 
of all, accounting for approximately 90 per cent of the late-summer hayfever. 

But the north-central flora also contains elements encroaching on it from the West 
and the South. Thus Russian thistle flourishes in some sections including parts of the 

Chapter IV 


Regional Surveys 

Chicago area and Indiana, and prairie ragweed or burweed marshelder, also a western 
species, occurs abundantly in and about Chicago where it is one of the most important 
local causes of hayfever. Western ragweed, a far-western species, is locally abundant 
in Iowa and parts of Illinois, and bur ragweed, a Rocky Mountain species, occurs in 
western Iowa, but neither of these two latter species is considered important except 
possibly in restricted localities. Reaching into this region from the Southwest occurs 

(Ohio, Kentucky, Indiana, Michigan, Illinois, Iowa, Eastern Missouri, Wisconsin and 

Southern Ontario) 

Acer saccharinum (Silver maple) 

Ulmus (Elms) 

Acer Negundo (Boxelder) 

Fraxinus americana (White ash) 

Populus* (Poplars) 

Quercus (Oaks) 

Juglans nigra (Black walnut) 

Carya (Hickories) 

Poa annua (Annual bluegrass) 

Poa pratensis (June grass) 

Dactylis glomerata (Orchard grass) 

Rumex Acetosella (Sorell dock) 

Plantago lanceolata (English plantain) 

Poa compressa (Canada bluegrass) 

Lolium perenne (Perennial ryegrass) . . 

Festuca (Fescue grasses) 

Phleum pratense (Timothy) 

Chenopodium album* (Lambsquarters) . . 

Agrostis alba (Redtop) 

Amaranthus spinosus* (Spiny amaranth) 
Amaranthus retroflexus* (Pigweed) .... 

Cynodon Dactylon* (Bermuda grass) 

Acnida tamarisc.* (West, waterhemp).. 
Chenopodium Botrys* (Jerusalem oak). 

Salsola Pestifer* (Russian thistle) 

Cannabis sativa* (Hemp) 

Humulus Lupulus* (Hop) 

Helianthus annuus* (Sunflower) 

Solidago (Goldenrods) 

Amb. psilostachya* (West, ragweed).... 

Artemisia caudata* (Wormwood) 

Ambrosia trifida (Tall ragweed) 

Ambrosia elatior (Short ragweed) 

Amb. bidentata* (South, ragweed) 

Cyclachaena xanthifolia* (Burweed) 

Xanthium* (Cockleburs) 

Iva ciliata* (Marshelder) 

Artemisia annua* (Annual wormwood) 
Artemisia ludoviciana (Prairie sage)... 





* Discussed in the accompanying paragraphs. 

western waterhemp. Its center of distribution is Oklahoma. In the north-central 
states it is regarded as an important factor in hayfever in many sections of Iowa, some 
of Illinois, and part of southern Indiana (BALYEAT and STEMEN 1927). Extending 
up from the South we find the southern ragweed including in its range almost the 
southern third of the north-central region, but, though frequently abundant enough to 
be a contributing factor in late-summer hayfever, its importance is largely overshadowed 
by the much more important short and tall ragweeds. Bermuda grass and spiny ama- 

Roger P. Wodehouse 176 Hay fever Plants 

ranth, two important hayfever plants of southern regions, occur in the extreme southern 
part but are scarcely ever abundant enough to be very important. 

Rough marshelder (Iva ciliata) occurs in the moist lowlands of the Mississippi 
and Ohio River valleys, and in East St. Louis and Cairo, 111., it is said to be an impor- 
tant cause of hayfever. Hemp is common in northern Illinois, including Chicago, and 
sometimes associated with it is the hop. Both are of only doubtful significance in hay- 
fever though they produce large amounts of anemophilous pollen. Sunflower is ex- 
tremely abundant in some parts of the region and is probably a local factor of occasional 
importance. Cocklebur occurs throughout much of the region but is of relatively little 
importance. Of the chenopods, lambsquarters occurs practically everywhere and sev- 
eral other members of the genus as Jerusalem oak (Chenopodium Botrys), and the oak- 
leaved goosefoot (C. glaucum L.) are locally abundant but have little or nothing to do 
with hayfever. 

The trees of this region appear to be less important than usual, only 7.3 per cent 
of the hayfever cases exhibiting symptoms from their pollen. The most important 
are ash, cottonwood, oak, maple and elm. Ash is common in the cities and it and 
several species of poplar or cottonwood, as the large-toothed aspen (Populus grandiden- 
tata), trembling aspen (P. trcmuloides) and the necklace poplar (P. deltoides) 
are common and of some importance in the Chicago region. Several species of oak are 
also abundant there, though not actually in the city. Eastern sycamore (Platanus occi- 
dentalis) also occurs commonly in the region and is regarded as a possible cause of 
hayfever in Illinois. Species of willow and birch are also found but appear to be of 
little importance. 

This region, comprising the north-central group of states and adjoining Canada, is 
so extensive that there may be considerable differences in the flowering periods of 
some of the plants in its southern and northern parts. The flowering of the trees and 
early grasses, the plants most affected by latitude, may be as much as two weeks earlier 
in the southern than in the northern part of the region, depending somewhat upon the 
season, while the late-flowering species, such as the ragweeds and goldenrods, may 
flower a little later in the southern than the northern part of the region. In other 
words, the summer season is longer in the southern part, starting earlier and ending 


The hayfever situation in most of the region of the north-central states has been 
adequately studied. HUBER (1926) recorded in tabular form all the hayfever plants of 
the region of Chicago and pointed out that Cyclachacna was abundant in certain sec- 
tions while not in others, and that it appeared to be invading the city from all direc- 
tions. Likewise he found that Russian thistle occurred abundantly enough in places 
to be included among his plants of primary importance, giving it a rating of 1 as com- 
pared with 4 for short ragweed. In his list of plants of secondary importance in the 
Chicago area are included bur ragweed, marshelder and cocklebur. HUBER also pointed 
out that, on account of the location of the city near Lake Huron and the peculiar topog- 
raphy of the surrounding terrain, the nature and severity of the hayfever was greatly 
influenced by wind direction and weather conditions. In the same year KOESSLER and 
DURHAM (1926) made a minutely detailed study of the hayfever situation in Chicago, 
dividing the city into blocks one mile square, each of which was studied separately. 
They found that 30 per cent of the city (40,000 acres) is allowed to run to weeds, 
largely ragweeds and hayfever grasses. They present in tabular form a pollen calendar 
of all the hayfever plants of the city and pollen counts of the most important species 
and show that the pollen of the ragweeds far outranked that of all others. 

FEINBERG and DURHAM (1933) found that 93 per cent of the hayfever cases in this 
region suffered from ragweed pollen, 53 per cent from ragweed pollen uncomplicated 
by that of other species, the grasses accounted for 45 per cent of the cases, but of these 
only 6 per cent had their symptoms confined to the grass season. Slightly more than 7 
per cent had definite hayfever from tree pollen, but of all such cases only one had 
symptoms confined to the tree season. Of the tree-sensitive cases 31 reacted to ash, 
21 to cottonwood, 14 to oak, 14 to maple and 3 to elm. Definite reactions were obtained 

Chapter IV 177 Regional Surveys 

in 32 cases to the pollen of Russian thistle, but in only a few of these was there reason 
to believe that this pollen was actually the major cause of their symptoms. 

These investigators observed that in many places the dominant weed was Cycla- 
chaena, and they made the very significant observation : "It is much more abundant now 
than it was eight years ago, but strangely enough has not become common except in 
the Chicago area". They also report that western waterhemp is common and increas- 
ing in the stockyard district but as yet is only a rare and local factor in hayfever. 
Among the grasses they find that June grass is the principal source of pollen, but 
Canada bluegrass is also an important contributor in the Chicago area. Among the 
trees, oaks, though not common in the city, occur abundantly near enough for their 
pollen to reach the city in considerable quantity. The tree-of-heaven (Ailanthus altis- 
sima) is commonly planted as a street tree and may be a minor factor in hayfever. 

DURHAM (1933a) reports a survey of the whole of Illinois. He points out that 
the state lies in the midst of the ragweed continental area, where there are 6,000,000 
acres of land devoted to the cultivation of wheat and small grains, and it is from these 
fields that the ragweed pollen comes, furnishing more than 95 per cent of the pollen 
in the air during the late-summer season. Cocklebur, he says, can not be of much im- 
portance though found throughout the state, but the annual and tall wormwoods 
(Artemisia annua and A. caudata) may be minor causes of hayfever. 

FIGLEY (1926) furnishes a pollen calendar of all the hayfever plants believed to be 
important in Ohio, and he states : "In a city such as Toledo the pollen that causes 
its inhabitants hayfever comes from the grass and weeds of the vacant lots and is not 
as a rule blown in from the rural districts". 

The hayfever situation of Indiana has been investigated by DURHAM (1929a, 
1935a). In the former publication the author furnishes a pollen calendar and table 
showing the relative importance of the various hayfever plants. It is to be noted that 
among the 30 or more plants listed spiny amaranth, western waterhemp, southern rag- 
weed and marshelder (Iva ciliata) are included but none of them ranked high in im- 
portance. In the latter publication DURHAM points out that ragweed constitutes 98 
per cent of the atmospheric pollen in the fall, and that Indiana is one of the worst states 
of the country for ragweed. 

A pollen survey for Ames, Iowa has been reported by COLES (1939). The situa- 
tion there is not different from the rest of the region, but this author finds hemp and 
western waterhemp abundant enough to be important in hayfever, with Kochia rapidly 
encroaching on the area. Mold spores also occur in significant quantity. Alternaria, 
Hormodendrum, rust and smut spores were encountered abundantly. 

The hayfever situation in Detroit has been investigated by WALDBOTT and STEERE 
(1931). The plants most commonly observed in the city were June grass, short rag- 
weed, goldenrod and quack grass. "Burweed marshelder [Cyclachaena], redtop and 
Russian thistle were seen in such small numbers in the fields that they should be con- 
sidered of local importance only". 

These authors state : "In some of the outlying communities where the weeds [plants 
of giant ragweed] were mowed by the village authorities, it was noticed that several 
days following the cutting, new growth made the pollination as profuse as before". 
This observation draws forcibly to attention the futility of the methods at present in 
vogue in combatting ragweed. 

The hayfever situation in Ontario has been investigated by DURHAM (1933c), 
LARUSH (1934) and DETWEILER and HURST (1930). The reports of the first two of 
these investigations are valuable contributions to the literature of hayfever. DURHAM'S 
report covers only the late-summer season, August 10 to September 30. He finds 
that, except in southern Ontario, the season is not long enough for the development 
of ragweed. In southern Ontario and Quebec he finds that the ragweed season begins 
about the middle of August, and by September 15 the air is almost free from the pollen. 
The ragweed pollen incidence at Toronto is about one third of that at Detroit and one 
eighth of that at Buffalo. Apparently virtually all of it comes from short ragweed; 
the giant is scarcely represented. 

LARUSH has accomplished a most remarkable piece of work, reported as "The 
Pollen Content of the Air in Toronto, Canada". This is a daily record for one year 

Roger P. Wodehouse 178 Hayfever Plants 

of atmospheric pollen caught on five slides exposed at each of seven different stations, 
that is to say 35 slides each day, together with "daily field observations from the time 
the early trees began to bloom until the first killing frost in the fall". Fifty eight differ- 
ent species of pollen were identified and counted on the slides, the identifications being 
made on the basis of their morphology checked by the record of the flowering of the 
plants in the field. Among the trees recorded are silver maple (April 2 to 11), red 
maple (April 15 to May 1), elm (April 21 to May 10), poplar (May 4 to 15), birch 
(May 11 to 29), oak (May 26 to June 11), ash (May 13 to 27), boxelder (May 7 to 
15). Of these the pollen counts of oak, elm and birch greatly outnumbered the others. 
Among the grasses recorded are June grass (June 8 to 19), but the grass pollen curve 
shows that it reaches effective quantities toward the first of June rapidly rising to its 
peak on June 19, and falling off with wide daily fluctuations to the end of Septem- 
ber. Among the weeds recorded are plantain (July 4 to Aug. 20), Chcnopodiaceae 
(July 14 to September 18), Artemisia biennis (August 26 to November 1), Artemisia 
caudata (August 7 to 24), short ragweed (August 16 to October 1). The pollen of 
the latter enormously outnumbers that of all others. The curve shows that ragweed 
pollen in Toronto reaches effective quantity about August 15, rises rapidly to its peak 
at about September 5, thereafter declining at first rapidly then slowly to the end of the 
month. An examination of LARUSH'S tables shows at a glance the complete story 
of practically every kind of pollen in the air, and the enormous number of observations 
upon which these tables are based is a guarantee of their accuracy. One leaves this 
remarkable report with a sigh of regret that there are not more such, and that death 
cut prematurely short so promising a career as that of its author. 

GROH and MINSHALL (1940), reporting on the ragweed situation in eastern Canada, 
state that the peak incidence of short ragweed pollen is found in Montreal and the region 
around the southern tip of Lake Ontario, while the northern parts of Ontario and 
Quebec are nearly free. The Gaspe peninsula is free and the Quebec Department of 
Agriculture is making a determined effort to keep it so. In Nova Scotia the authors 
find the rich agricultural region of the Annapolis Valley to be heavily infested with 

The hayfever situation of the North Central Region, and the literature pertaining 
to it have been briefly but effectively summarized by HANSEL (1936) and VAUGHAN 
(1931, 1939) and more fully by DURHAM (FEINBERG 1934) together with additional 
observations by these investigators not previously reported. 

FASSETT, McGARY and BATES (1938) have compiled a sort of atlas of what are 
stated to be the hayfever plants of Minnesota, Wisconsin, Iowa, Illinois, Missouri and 
Indiana, showing by maps their distribution within these states. The figures are largely 
reproductions from standard botanical texts and the maps are compilations from similar 
sources. Their conclusions, they state, are based on THOM MEN'S five postulates and 
"the results of tests made on more than 600 pollen sensitive cases". 

V. The Southern States (Florida, Tennessee, Georgia, Alabama, 

Mississippi, Louisiana, Arkansas, Southern Missouri, Oklahoma 

and Eastern Texas) : 

Juniper us. Mountain cedar (/. mexkana) occurs only on the lime- 
stone hills of Texas, but is especially abundant in the neighborhood of 
Austin and Dallas where it has proved to be one of the most important 
hayfever plants, accounting for hundreds of cases of midwinter hayfever. 
Other species of juniper also occur in the southern area; the red cedar 
(/. virginiana) is abundant, reaching its maximum development in the 
"Cedar Glades" of Tennessee and northern Alabama. 

Corylus. Two species of hazel (C. americana and C. rostrata) are 
abundant locally, the latter especially in the mountains of Georgia. 

Popuhis. Several species of cottonwood or poplar, including P. del- 

Chapter IV 179 Regional Surveys 

toides and P. alba, are abundant and have been recorded as important in 
Memphis, parts of Alabama and San Antonio. 

Betula. The principal birch of the South is the red or river birch 
(B. nigra) extending almost throughout the region, from Florida to eastern 
Texas. B. lenta is also found in the northern part. 

Quercus. Many species of oak occur, and in most places they are the 
commonest trees, contributing the greater part of all the tree pollen. One 
of the commonest is the live oak (Q. virginiana) extending almost through- 
out the South, but especially characteristic of Texas where it is regarded as 
one of the most important hayfever trees (KAHN and GROTHAUS 1930). 
The black-jack oak (Q. marilandica) is the most abundant tree of Oklahoma 
but is there regarded as only a minor cause of hayfever. Q. alba and Q. 
rubra are considered to be important in Alabama (WEIL 1931, 1937). 
Most oaks are so closely related that their pollens are generally regarded 
as interchangeable, but KAHN and GROTHAUS (1930) state: "Live oak 
has been our local factor, the other oaks of our community [San Antonio] 
often giving negative skin tests in our positive oak cases'*. 

Carya. Several species of hickory are common throughout the South 
but by far the most important is pecan. It is especially abundant in the 
southern part of Georgia, Alabama and Mississippi where it is frequently 
the cause of a very severe type of hayfever. C. ovata, C. laciniosa Loud., 
C. glabra and C. alba also occur in various parts of the South. 

Tricholaena rosea. Natal grass is abundant in parts of Florida and 
occurs sparingly at other places in the Gulf states but is of little or no 
importance in hayfever. 

Ligustrum. The privets are undoubtedly an important factor in hay- 
fever and are reported as such in New Orleans (THIBERGE 1934). Several 
species are involved. See p. 121. 

Phleum and Dactylis. Timothy and orchard grass occur only in the 
northern part of the region. For example in Memphis and vicinity where 
both are reported as important (LACKEY and GOLTMAN 1934). 

Amaranthus. Carelessweed is found in quantity only in southern 
Texas where it is regarded as moderately important. Of probably greater 
importance is the spiny amaranth. In the northern part of the region it 
blooms from June to August or September, but in the southern part, as at 
New Orleans, it blooms practically throughout the year. HEINBERG (1930) 
has shown that in Florida (Pensacola) it may be the sole cause of a severe 
type of hayfever. In many other parts of the South it is probably a con- 
tributory cause of considerable importance. It is mentioned in Alabama 
as such (WEIL 1931), the Gulf states (SCHEPPEGRELL 1916a), and in New 
Orleans (PENFOUND, EFRON and MORRISON 1930). Amaranthus retro- 
flexus and A. hybridus are common practically throughout the southern 
area but are unimportant. 

Acnida tamariscina. Western waterhemp is one of the most important 
plants in Oklahoma and adjacent part of Texas (BALYEAT and STEMEN 
1927) but outside of this region is scarcely anywhere abundant enough to 
be a factor in hayfever. 

Roger P. Wodehouse 


Hayfever Plants 


(Tennessee, Georgia, Florida, Alabama, Mississippi, Louisiana, Arkansas, Southern 
Missouri, Oklahoma and Eastern Texas) 
















Juniperus mexicana* (Mountain cedar) 







Alnus rugosa (Smooth alder) 



TJlmus alata (Winged elm) 





Corylus* (Hazel) 


Taxodium distichum (Bald cypress) 
Populus* (Poplars, Cottonwoods) 



Acer (Maples) 




Acer Negundo (Boxelder) 


Betula nigra (Red birch) 



Betula* (Birches) 


Quercus* (Oaks) 




Salix (Willows) 




Morus (Mulberries) 



Maclura pomifera (Osage orange) 
Celtis laevigata (Southern hackberry).. 
Liquidambar Styraciflua (Sweetgum). . . 
Platanus occidentals (Sycamore) 
Fraxinus americana (White ash) 
Carya Pecan (Pecan) 






Carya* (Hickories) 






Juglans nigra (Black walnut) 




Poa pratensis (Junegrass) .... 






Paspalum dilitatum (Dallis grass) 
Tricholaena rosea* (Natal grass) 
Plantago lanceolata (English plantain) 
Rumex Acetosella (Sorrel dock) 






















Broussonet. papyrif. (Paper mullberry).. 
Lolium perenne (Perennial ryegrass) . . . 
Lolium multiflorum ( Wintergrass) 
Dactylis glomerata* (Orchard grass)... 
Festuca octoflora (Six- weeks fescue) 
Cynodon Dactylon (Bermuda grass) 























Sorghum halepense (Johnson grass) 
Amaranthus spinosus* (Spiny amaranth) 

Amaranthus retroflexus* (Pigweed) 
Amaranthus Palmeri* (Carelessweed).. 
Acnida tamarisc. (West, waterhemp) . . . 
Chenopodium album (Lambsquarters). . . 
Chenopodium ambrosioides (Mex. tea).. 
Chenopodium Botrys (Jerusalem oak)... 













i! 11 







Amb. psilostachya* (West, ragweed).. 
Ambrosia bidentata* (Southern ragweed) 
Ambrosia trifida (Tall ragweed) 











Ambrosia elatior (Short ragweed) 

Ambrosia hispida (Seashore ragweed).. 
Ambrosia aptera (West, giant ragweed) 

Cyclachaena xanthifolia* (Burweed) 
Xanthium speciosum* (Great clotbur).. 
Xanthium* (Cockleburs) 























Iva frutescens* (Common marshelder).. 





Iva angustifolia (Marshelder) 
Artemisia annua* (Annual wormwood).. 






* Discussed in the accompanying paragraphs. 

Chapter IV 


Regional Surveys 

Table V. Concluded: 

Salsola Pestifer* (Russian thistle) 

Ulmus serotina* (September elm) 

Ulmus crassifolia* (Cedar elm) 

Sorghastrum nutans* (Indian grass) 

Baccharis halimifolia* (Groundsel bush) 
Casuarina* (Australian pine) 



* Discussed in the accompanying paragraphs. 

Ambrosia. The two principal ragweeds, as in the eastern states, are 
the tall and short. The former is found almost throughout the eastern part 
of the southern area but does not extend in effective quantity west of Okla- 
homa City. In the extreme southern part of the area, as in parts of Florida 
and New Orleans, the plants flower almost all summer, starting in May or 
earlier, but they shed much less pollen than in the East. Tall ragweed is 
not found in Florida nor the southern part of Georgia and Alabama, and 
from the Mississippi valley westward is largely replaced by the Texas great 
ragweed (A. aptera). Southern ragweed occurs on the prairies and in- 
terior low plateaus from western Mississippi and Tennessee westward in- 
cluding Arkansas and Oklahoma. Western ragweed is found from the 
Mississippi River westward but is not important except in western Okla- 
homa and the southernmost part of Texas (DURHAM 1933&). 

Cyclachaena. Prairie ragweed "is found in the South principally in 
the panhandle of Oklahoma, in Texas and the northern corner of Missouri" 
(DAVISON, LOWANCE and DURHAM 1934). It is also recorded in Arkan- 
sas (LACKEY and GOLTMAN 1934). 

Xanthium. Various species of cocklebur are common throughout the 
region but for the most part they are unimportant. The great clotbur 
(X. speciosmn), however, sheds much more pollen than most species and 
is common in the Mississippi valley and westward. 

Iva. Rough marshelder is found almost throughout the South from 
the western part of Georgia westward. Narrow-leaved marshelder is found 
in Arkansas, Oklahoma and Texas. In southern Oklahoma and eastern 
Texas it is regarded as an important local factor in hayfever (DAVISON, 
LOWANCE and DURHAM 1934). 7. jrutesccns grows only in the tidal 
marshes along the coast. In such places it may occasionally be a minor local 
factor in hayfever. 

Artemisia. The mug worts and wormwoods are of relatively little im- 
portance in the southern area, though several species occur. A. annua is 
found in most places, exclusive of Oklahoma, Louisiana and Texas, and 
A. vulgaris occurs fairly abundantly in parts of Alabama and Georgia. 

Salsola. Russian thistle occurs in appreciable quantity only in Okla- 
homa and adjacent parts of Texas. 

Roger P. Wodehouse - 182 Hayfever Plants 

Ulwius. Scrub or cedar elm ( U. crassifolia) occurs from Mississippi 
to central Texas. Flowering at about the same time as the ragweeds, it 
occasionally complicates late-summer hayfever. September elm (U. sero- 
tind) occurs in Georgia, Alabama and Tennessee but appears to be rarely 
common enough to be of any importance (BLACK and DURHAM 1930). 

Sorghastrum nittans. Indian grass is found in dry places throughout 
the South, and in the prairie regions of the Mississippi valley it was for- 
merly one of the most important tall prairie grasses but its numbers have 
been decimated through agricultural operations. It is probably much less 
harmful than the weeds that have largely taken its place, but it is regarded 
as having hayfever possibilities in Florida (NicnoL and DURHAM 1931) 
and elsewhere by other investigators. 

Baccharis halimifolia. Groundsel bush occurs along the coast from 
Florida to Texas and is particularly abundant in parts of Florida where 
it is regarded by NICHOL and DURHAM (1931) as a possible cause of 

Broussonetia papyrijera. Paper mulberry appears to be a local cause 
of hayfever as far west as Oklahoma and Texas (BALYEAT and RINKEL 

Casitarina. Several species of Australian pine are extensively planted 
in Florida especially along the beaches and water ways as sand binders. 
C. Cunninghamia is particularly abundant in and around St. Petersburg 
and Tampa, where it flowers in September and October. Though its pollen 
has marked hayfever characteristics it is reported by METZGER (1939) to 
be of no importance in hayfever. On the other hand ZIVITZ (1942) states 
that in the region of Miami, where C. equisetifolia and C. lepidifolia are 
abundant, their pollen does cause some hayfever. On the Gulf coast the 
casuarinas flower profusely in September and October. But on the east 
coast they are reported to flower in March, April and December. 


Much excellent work has been done to discover the causes of hayfever in the South, 
but the problem is extremely complicated by the size of the region and the variety of 
conditions encountered. Most of the studies are local, dealing with single states, parts 
of states or single cities. But WODEHOUSE (1941) gives a general discussion of the hay- 
fever situation in the South. DAVISON, LOWANCE and DURHAM (1934) have made a 
study of the huge southern area "which reaches from the lower borders of Pennsylvania 
and New Jersey on the north to the Florida keys and from Chesapeake Bay and Cum- 
berland Sound on the east to the western part of Texas". 

Also of general application is the report by DURHAM (1933&) on the ragweed sit- 
uation in the Southern states. He finds that the only ragweeds of major importance 
are the tall and short. 

Oklahoma. BALYEAT through surveys of the Oklahoma flora in association 
with T. R. STEMEN finds that the trees are relatively unimportant, the commonest 
being the necklace poplar (Populus deltoides} flowering from April 5 to 26, and 
black-jack oak (Quercus marilandica) April 15 to May 1, the latter the commonest 
tree in the state. The grasses are principally Bermuda and Johnson grass. Among the 
weeds Russian thistle, lambsquarters and pigweed are found to be abundant, but of 
much greater importance is western waterhemp. Tall, short and western ragweeds 
they find to be accountable at least partly for about 73 per cent of all cases. Minor 
causes are considered to be rough marshelder, cocklebur, corn, and gray sage (Artemisia 

Chapter IV 183 Regional Surveys 

A detailed study of the hayfever plants of Tulsa county and adjoining territory of 
Oklahoma is reported by DENNY and TENNY (1932). 

Alabama. The hayfever situation in Alabama has been extensively studied by 
WEIL (1931, 1937). In the earlier report is furnished a pollen calendar prepared es- 
pecially for Montgomery but designed to apply more or less exactly to the whole state, 
and in the latter is furnished a complete list of Alabama plants which have hayfever 
possibilities. WEIL states that he is convinced that there are hundreds of cases of pecan 
hayfever in Alabama that : "Patients who are sensitive to pecan pollen usually have 
symptoms at least as severe as those due to ragweed pollen and frequently more severe. 
Half of the cases had asthma as well as hayfever". The pollen is found in the air from 
the middle of April to the latter part of May. Hickory and black walnut are also 
important, but their pollens interreact with each other and with that of pecan so that 
"immunization against one will protect against all three." 

Among the grasses WEIL finds the most important to be rye grass, Bermuda grass 
and Johnson grass, but only half of the summer cases occurring between May and 
September were found to be due to grass pollen, the others being due to some as yet un- 
known cause. 

Late-summer hayfever, occurring from September 1 to frost, was found to be due 
almost entirely to tall and short ragweed with cocklebur a minor contributing factor. 
Spiny amaranth is also considered to be a factor at this time, since it is abundant in the 
region and flowers at about the same time as the ragweeds and about 40 per cent of the 
hayfever patients react to its pollen. 

Tennessee. SPITZ (1927) and BOWIE (1939) reporting from Nashville, point out 
that hayfever occurs there in three seasons. The early-spring season extends from 
about the end of February to the middle of May and is due to cottonwood walnut, 
birch, elm, maple, willow and "cedar" ; the summer hayfever season extends from the 
middle of April to the end of summer, and is due to the pollen of grasses of various 
kind, including Bermuda and Johnson grass ; and the late-summer hayfever season ex- 
tends from the end of July to frost and is due almost entirely to the ragweeds. 

HENRY and HERRING (1930) have furnished a botanical survey of Memphis and 
surrounding territory within a radius of 200 miles. This area includes the eastern end 
of Tennessee and adjacent corners of Kentucky, Mississippi, Arkansas and Missouri. 
For this region the authors list, with their times of flowering, some 80 species of plants 
with hayfever possibilities. They point out that Russian thistle does not occur in this 

HENRY (KAHN and GROTHAUS 1930) gives an abbreviated list of the more im- 
portant hayfever plants of Memphis, stating that probably the most abundant tree of 
the region is oak, and that the first trees to flower in spring are the elms starting 
about the first week in February. 

LACKEY and GOLTMAN (1934) in a hayfever survey of the Memphis area list, with 
their flowering periods, about 90 species which might be suspected of causing hayfever. 
They point out that a large variety of plants is encouraged by the geographical variety 
of the region, comprising the delta, loess bluffs and north central plateau, all presenting 
widely different natural floras. However, the dominant flora existing at present 
throughout most of the region is so much the result of human interference that natural 
ecological factors are less important than would otherwise seem. 

Louisiana. Almost the earliest work done in the United States on the botanical 
aspect of hayfever was that of SCHEPPEGRELL (1916a, 1916b) at New Oraleans. Later 
this work was extended to include the whole of the United States and published by 
SCHEPPEGRELL (1922) in his book on Hayfever and Asthma, but these pioneer works 
are now mainly of historical interest. 

A study of the hayfever situation in New Orleans has more recently been made by 
PENFOUND, EFRON and MORRISON (1930). They say that the city presents the maxi- 
mum of hayfever and asthma hazard because of the long and favorable growing season 
and because approximately 70 per cent of the land is abandoned to weeds. There is so 
little frost, occurring only from December 7 to February 14, that allergic diseases due 
to pollen may exist throughout the year. The maximum for most cases, however, oc- 

Roger P. Wodehouse __184 Hay fever Plants 

curs from July to September. Their report of a botanical survey of the city of New 
Orleans and some of the surrounding suburbs lists with their relative abundance about 
60 species of weeds exclusive of trees, which are known to cause hayfever or have 
hayfever possibilities. New Orleans is predominantly a region of grasses, the common- 
est being Bermuda grass with a flowering period from April to December, and it con- 
stitutes the greatest hazard in pollen allergy. Also extremely abundant are two species 
of Paspalum known as bull grasses, P. dilitatum, tall bull grass or Dallis grass, and P. 
Vaseyanum, hairy bull grass, both flowering from April to November. Also important 
is the tall ragweed, flowering from July to December and to a lesser extent short rag- 
weed flowering at about the same time. The pollinating periods of many hayfever 
plants in New Orleans are variable depending upon weather and human influences such 
as cutting of grass and weeds, and soil disturbances. "It is recognized also that perhaps 
40 per cent of the species may, during years of favorable conditions, bloom throughout 
the entire year". Consequently hayfever does not fall into well marked seasons as it 
does farther north. Some of the hayfever plants can be classed as winter bloomers, 
spring bloomers, autumn bloomers and ever bloomers. The most important are the 
latter, effective from early April to December. 

THIBERGE and HAUSER (1931) present a list of common plants with hayfever possi- 
bilities showing their time of flowering, distribution and the size and shape of their 
pollen grains. This study, however, does not apply especially to the plants of Louis- 
iana, though reported from New Orleans, but is rather of nation wide scope. The 
authors draw attention to an interesting case of Clematis hayfever discovered by finding 
pollen grains on slides exposed in the patient's sleeping room. In a later paper 
THIBERGE (1934), in discussing trees suitable for planting in the South, points out 
that several species of privet, as they are commonly grown there, permitting the plants 
to go untrimmed and bear flowers, are important causes of hayfever. 

Florida. NICHOL and DURHAM (1931) report the result of a botanical survey 
and the daily record of pollen caught on oiled slides at Miami over a period of two 
years. They record unusually low pollen counts which they attribute to the lack of 
extensive agricultural areas and to the fact that the prevailing winds during the summer 
and fall are from the ocean. The authors also furnish a list of the wind pollinated 
plants of Miami with their dates of flowering. It is interesting to notice that some of 
these, as cocklebur and the palms, are not represented at all in the pollen record, and 
others, as pine and oak, are only poorly represented in spite of their abundance in the 
vicinity. This suggests that the prevailing ocean breeze is the principal determining 
factor in the low pollen incidence. 

The grasses in Florida are believed by NICHOL and DURHAM to be the principal 
cause of what little hayfever there is. Bermuda and Natal grass are suggested as the 
most important, flowering throughout the year except January and part of February. 
Next in importance they consider to be Johnson grass with a flowering period almost 
as long. There is no giant ragweed but the dwarf ragweed flowers from May to Oc- 
tober. Ragweed plants on account of their long growing season reach abnormally 
large proportions but shed relatively little pollen. As a result of their studies they 
conclude that : "The sea coast of Florida is just about as nearly perfect for ragweed 
hayfever sufferers as any place could be". 

METZGER (1932, 1939) finds that, while the beaches of the east coast of Florida may 
be essentially free from ragweed pollen, this is unhappily not true of the west coast. 
Sarasota, Arcadia and Tampa, he finds, have sufficient ragweed to cause trouble. "The 
west coast of Florida is now undergoing the sad experience that many of the Michigan 
hayfever resorts had . . . Since I have become weed conscious, I notice each year a 
definite increase in ragweed". 

Eastern Texas. The earliest contribution to our knowledge of hayfever in Texas 
to be found in the literature is that of KEY (1918). He reported the cause of winter 
hayfever, which makes its appearance between the middle of December and Christmas 
and lasts until the middle of February, to be the pollen of mountain cedar. The extra- 
ordinary prevalence of this type of hayfever in the parts of Texas where the cedar 
grows is the outstanding characteristic of hayfever in Texas. 

Chapter IV 185 Regional Surveys 

HULSEY (1933) reporting from Fort Worth, records the atmospheric pollen counts 
over a period of three successive years, showing mountain cedar from December 9 to 
February 1, elm from March 1 to May 5 and again in September and October, cotton- 
wood from March 15 to April 15, Oak from March 21 to May 1, ragweed from Sep- 
tember 1 to November 10, and grass pollen occurring in small amounts all through 
the year. There is found, however, considerable variation in the flowering periods from 
year to year, mountain cedar pollen sometimes being caught as early as November 4 and 
ragweed as late as December 31, and both causing symptoms of hayfever. 

KAHN and GROTHAUS (1930) in their study of tree-pollen hayfever in the South 
find that "The tree pollen causing the largest amount of distress in any of the southern 
states is that of the mountain cedar. Its annual victims can be numbered by the 
thousand". Otherwise they find that pure tree-pollen hayfever is very rare. But tree 
pollen complicating hayfever of other origin is much commoner, often severe and 
generally multiple. In San Antonio the most important trees they found to be pecan, 
flowering from March 30 to May 9, and live oak, from March 9 to May 6. Others 
of considerable importance are ash, cottonwood, willow, several species of oak, hack- 
berry, boxelder and sycamore and, in Dallas, elm. KAHN (1924, 1926) reports the 
results of exposing atmospheric pollen slides. "The process", he says, "is exceedingly 
satisfactory and no more difficult than the examination of an ordinary microscopical 
urinary sediment". He finds that in San Antonio grass pollen remains in the air 
practically throughout the year, though never in very large amounts. Still it is suffi- 
cient to make grass hayfever perennial. The amaranths, carelessweed and pigweed, 
are important in southern Texas rather than the ragweeds during the late summer. 
The ragweeds, Ambrosia trifida and A, psilostachya, they find "are moderately profuse 
but owing to the dry months of late July and August, they do not pollinate to any 
extent until the middle of September". But during this period ragweed pollen in 
southern Texas never exceeds that of the grasses, though in northern Texas the reverse 
is true. 

FRENCH (1930) reporting from Fort Sam Houston, finds that the principal causes 
of hayfever are Bermuda grass, Johnson grass, tall ragweed, short ragweed, pigweed, 
carelessweed, plantain and mountain cedar, the latter being a frequent cause indoors 
when used as Christmas trees. 

Summer Hayfever of Unknown Origin: In spite of the unusually large number 
of pollens which have been shown, or suspected, to cause hayfever in the South, prob- 
ably more than half of the summer hayfever cases still remain unexplained. WEIL 
(1937) reports from Alabama that out of a group of 22 cases of summer hayfever 12 
failed to react to pollen or any other allergen with which he tested them, and when 
treated with grass pollen, as non-reactors, failed to be benefited. He states : "It must 
be admitted that we do not yet know the cause of over half of the cases occurring 
in the summer months." Later WEIL (1940) reports the study of 47 such cases occur- 
ring between May and September or October. 

Allergists have lately come to recognize this type of hayfever as a definite entity 
peculiar to the South caused by an unknown factor or possibly several unknown fac- 
tors, hence it is called "Summer Hayfever of Unknown Origin" or more recently, 
"X hayfever". The symptoms are characteristic of hayfever and asthma caused by 
pollens. They begin usually in May and persist throughout the summer, gradually 
tapering off toward the end of September or the beginning of October. There is diurnal 
variation in the symptoms; most cases are worse at night and early morning, often 
nearly or quite free in the afternoon. Some patients maintain a degree of freedom by 
remaining in an air conditioned room while others are not benefited at all by air con- 
ditioning, finding themselves worse indoors than out. All are immediately relieved 
by leaving the infested area, generally going to the coastal beaches. 

In an endeavor to discover the distribution and prevalence of X hayfever both 
EFRON and the present writer sent out questionnaires to all of the allergists of the 
South who could be contacted. To both the responses were most gratifying. Accord- 
ing to the answers received the distribution of X hayfever approximately coincides 
with the southern coastal plain with a northward extension along the Mississippi delta 
to the southwestern tip of Kentucky. Roughly this includes the southern part of South 

Roger P. Wodehouse 186 Hayfever Plants 

Carolina, the southern two thirds of Georgia and Alabama, northern Florida, the west- 
ern tip of Tennessee, Mississippi, Louisiana, and southeastern Texas. The questionnaire 
also brought out the fact that X hayfever is more prevalent in the southern reaches 
of this area than in the northern, reaching a maximum of 65 per cent of all hayfever 
cases in New Orleans. 

So important and so baffling has proved the problem of X hayfever that a group of 
allergists of the South has formed itself into the Committee of Allergists for the Study 
of the Unknown Causes of Hayfever (BOWEN 1941). The Committee is headed by 
RALPH BOWEN of Houston, Chairman, and B. G. EFRON of New Orleans, Secretary. 
In announcing the formation of the Committee BOWEN states that the following are not 
of etiological importance: "1. Pollens, 2. Johnson smut, 3. Air borne fungus spores that 
are readily cultured on artificial media; such as Alternaria, Hormodendrum, Aspergil- 
lus, etc. . . . The Committee welcomes corresponding members". 

Further activities of the Committee are reported by EFRON (1942-1943). They 
have investigated the possibility of insect emanations as the cause of X hayfever, testing 
cases with extracts of 17 different insects, including such as the large American roach 
which is extraordinarily abundant in the South, the citrus white fly, midge and others 
which occur in the infested area. Positive skin tests were obtained from the insect al- 
lergens with 25 per cent of the X-allergic cases tested. However, the reactions were 
not specific ; those individuals who reacted to one insect reacted to the others. And since 
the incidence was lower than would be expected, and insects are ubiquitous, they are not 
to be considered the answer to the X hayfever problem. So this line of attack is to be 
abandoned by the Committee. 

A later report from the Committee of Allergists for the Study of Unknown Causes 
of Hayfever (1943) shows a return to the unfinished investigation of fungus spores 
as a possible cause of X hayfever. The spores were collected from infected air 
by means of the Wells air centrifuge and picked directly from the celluloid strips 
by means of a micromanipulator and grown as single spore cultures. Others were 
washed off with sterile distilled water and plated out in the usual way. Cultures 
were grown on potato-dextrose agar. Extracts made from the pellicles obtained 
from 10 species of fungi were tested on X-hayfever cases. Positive skin reac- 
tions comparable in size with those obtained from pollen extracts with hayfever cases, 
were obtained with extracts of Fusarium, Helminthosporiwn, Cladosporium, Tricho- 
derma and Alternaria. The Committee concludes, however, that : "Although it is ap- 
parent that these molds are not the etiologic agents responsible for X hayfever and 
asthma, further investigation of fungi is justified by the data already obtained." From 
the work of such an active and determined group of investigators as this Committee 
of Allergists, there is good reason to hope that the etiologic factor of X hayfever will 
eventually be discovered. 

Fungi : There is no doubt that mold spores play an important part in asthma 
and hayfever of the South, though perhaps not more so than elsewhere. PRINCE, SELLE 
and MORROW (1934) and PRINCE and MORROW (1937) have shown that mold sensitiza- 
tions in Galveston are more likely to be manifest in the winter months, and "an in- 
crease in the mold content of the air is actually encountered in the winter when the 
moisture is conducive to the growth of fungi". These authors have shown that when 
the wind blows from the north and northeast the count of mold spores at Galveston 
greatly increases, and when the wind blows off the Gulf the spore count drops almost 
to zero. This they attribute to the extensive marsh land to the north and northeast 
of the island. They found many hayfever and asthma patients sensitive to such forms 
as Monilia, Penicillium, Aspergillus, Trichoderma, Helminthosporium, Hormodendrum, 
Cladosporium and some unidentified species. And treatment with extracts of these 
proved satisfactory in most cases. 

Encouraged by these results a group of allergists formed themselves into the Asso- 
ciation of Allergists for Mycological Investigations, for the purpose of extending these 
investigations to include air-borne molds in central and southwestern United States. 
The first report of the Association has been published by MORROW, LOWE and PRINCE 
(1942). It deals with the atmospheric mold spores from widely separated stations, in- 
cluding El Paso, Abilene, Fort Worth, Dallas, Waco, Temple, San Antonio, Houston 

Chapter IV 187- Regional Surveys 

and Galveston in Texas ; Shreveport in Louisiana ; Little Rock in Arkansas ; Nashville 
in Tennessee; St. Louis and Kansas City in Missouri; Minneapolis in Minnesota; 
Milwaukee in Wisconsin; Evanston in Illinois; and Toledo in Ohio. At each of the 
stations agar plates were exposed at semimonthly intervals. The molds which could be 
cultured from these were identified by experts in the groups to which they belong. In 
addition to those species recorded for Galveston, such forms as Alternaria, Spondilo- 
cladium, Fusarium, Mucorales and Pullularia were prominent. The dominant forms 
were found to be Alternaria and Hormodendrnm, occurring more frequently and in 
higher numbers than any other molds and reaching their maxima in the winter months. 
Aspergillus and Penicillium also occurred frequently but more or less uniformly 
throughout the year. Pullularia when present occurred as a "shower" making up the 
major part of the total count for the station. 

These investigators found no significant differences between the northern and 
southern stations which could throw light on the X hayfever of the South. In fact 
the spore counts from the northern stations were even higher than those from the 

The Association is continuing its work and promises an early report of further 

Hayfever Resorts: Most hayfever sufferers are able to secure a measure of relief 
by going to the mountains of northern Georgia and the Carolinas, or to the beaches. 
EFRON (1942-1943) lists Savannah, Brunswick and Jacksonville beaches, Panama City, 
Biloxi, Gulfport, Pass Christian and Galveston as short resorts at which patients with 
X hayfever may find relief. These are likewise credited as resorts for victims of hay- 
fever from ragweed and other pollen. For the most part the beaches owe their com- 
parative freedom from pollen to the fact that the wind at these places generally blows 
off the ocean. Their chances of freedom are much greater when the resorts are well 
separated from the mainland by intervening water or marsh land, which is often the 

In Georgia both Savannah and Brunswick beaches offer partial or complete relief 
from pollen and X hayfever. In Florida, Jacksonville Beach offers a measure of relief 
but some patients who find themselves benefited at Savannah Beach have reported no 
benefit at Jacksonville Beach. This is probably because the extensive areas of marsh 
land originally separating the beach from the mainland have now been largely filled 
in and bear a flourishing crop of weeds. Most of the beaches along the east coast of 
Florida can justly claim a high degree of immunity. Miami Beach appears to be vir- 
tually free from hayfever pollen. This is because the wind here nearly always blows 
off the ocean and the beach is well separated from the mainland by a large inlet from 
Biscayne Bay. Places close by on the mainland, such as Miami and Coral Gables are 
by no means free from hayfever on account of the large weedy areas surrounding them. 
Key West can quite justly claim almost complete immunity from hayfever. This, 
however, is entirely due to its insular position, for ragweed can be found flourishing 
in and around the city itself. But being an island Key West always has a sea breeze. 

Panama City claims a degree of freedom from hayfever, especially that of the X 
type. Such immunity that it possesses, however, is largely due to the fact that the 
prevailing winds are from the Gulf, and much of the region to the landward of the 
City is open water and marsh land. The City itself has an abundance of vacant lots 
fully occupied by short ragweed and other hayfever weeds. Pensacola can not be re- 
garded at all favorably as a hayfever resort. It is one of the weediest cities on the 
Gulf Coast. 

In Mississippi Biloxi, Gulfport and Pass Christian all claim a high degree of im- 
munity from hayfever of both the X and the recognized pollen types. Biloxi is perhaps 
the best situated since it is separated from the mainland by considerable open water 
and marsh land, but in the main these resorts depend upon the breezes from the Gulf 
to keep them supplied with pollen-free air since they themselves are badly infested 
with hayfever weeds. 

Galveston claims a degree of immunity from both the X and recognized pollen types 
of hayfever owing to the fact that it is an island and largely supplied with pollen-free 
air from the Gulf. 

Roger P. Wodehouse 


Hayfever Plants 

VI. The Southwest (Arizona, New Mexico, Western Texas) : 

Hayfever in the Southwest is more severe and more complicated than 
in most other regions. It is also more of a local problem. The settlements 

(Arizona, New Mexico, Western Texas) 















.? - 

\ 1 




Juniperus mexicana* (Mountain cedar). 

Juniperus* (junipers) 






Populus* (Cottonwoods) 





Fraxinus Xoumeyi* (Arizona ash) 




Quercus* (Oaks) .... 




Olea europaea (Olive) 


Proscpis julifloia* (Mesquite) ... . 





Lolium perenne (Perennial ryegrass)... 
Bromus* (Brome grasses) 







Cynodon Dactylon* (Bermuda grass) 
Sorghum halepense (Johnson grass) 
Distichlis spicata* (Salt grass) 
Poa pratensis* (June grass) 







Illl II 

ill! !l 

Illl I 

i mi 

i mi 

i in 





Bouteloua* (Grama grasses) 
Chloris virgata* (Finger grass) 
Agropyron Smithii (Bluestem) 


Illl 1 
Illl 1 

i u 
i mi 


Koeleria cristata (Western Junegrass).. 
Amaranthus retroflexus (Pigweed) 
Amaranthus spinosus* (Spiny amaranth) 
Amaranthus Palmeri* (Careless weed) . . 
Amaranthus graecizans* (Tumbleweed) 
Acnida tamarisc. (West, waterhemp). . . 
Chenopodium album (Lambsquarters).. 
AtHplex Wrightii (Annual saltbush) . . . . 
Atriplex canescens (Wingscale) 









1 II 
till II 
Illl II 
Illl II 


n in 








1 III 



Atriplex* (Saltbushes) 
Salsola Pestifer* (Russian thistle) 







Kochia scoparia* (Burningbush) 
Kochia americana (Redsage) 


ill 1 



Allenrolfia occidentalis (Burroweed) 
Helianthus annuus (Sunflower) 
Artemisia tridentata* (Sagebrush) 



ii ii 




Artemisia filifolia (Silvery wormwood) . . 
Artemisia dracunculoides (Dragon sage) 
Artemisia gnaphalodes (Prairie sage).. 
Artemisia Wrightii (Gray sage) 
Artemisia Bigelovii (Dwarf sagebrush). 
Artemisia camporum (Field sagewort).. 
Artemisia frigida (Pasture sage) 
Ambrosia psilostach. (West, ragweed) 
Ambrosia aptera (West, giant ragweed) 
Franseria ambrosi. (Canyon ragweed).. 
Franseria deltoidea (Rabbit bush) 
Franseria dumosa (Bush sandbur) 
Franseria discolor (Low ragweed) 
Franseria acanthicarpa (Bur ragweed) . . 
Franseria tenuifolia (Slender ragweed) . . 
Hyinenoclea Salsola* (Greasebush) .... 
Hymenoclea monogyra (Jecote) 











mi ii 
ii ii 


ii ii 

ii ii 


u mi 
i u 

, M 

ii i i 
u 1 1 

n f 

ii mi 
n in 










Dicoria Brandegei (Dicoria) 



Dicoria canescens (Dicoria) . . 


mi ii 

ii n 



Iva axillaris (Poverty weed) 



mi u 

n in 

Cyclachaena xanthifolia* (Burweed) . . . 
Xanthium (Cockleburs) 

ii ii 

'i Hi, 


* Discussed in the paragraphs immediately following. 

Chapter IV 189 Regional Surveys 

of the arid regions generally owe their existence to irrigation, which pre- 
sents conditions favorable to the growth of hayfever plants. Within rela- 
tively short distances widely varying types of flora may be encountered 
owing to differences in elevation as well as to conditions of irrigation. 
Moreover the dry atmosphere which prevails throughput most of the region 
favors pollination by wind, resulting in a greater proportion of the vegeta- 
tion being anemophilous than is encountered in regions of heavier rainfall. 
WILSON (1934) has found a large proportion of the victims of hayfever 
much larger than in most other regions to show no family history of 
allergic manifestations, from which it is to be inferred that the atmospheric 
conditions are such that persons in this region, even without predisposing 
causes, may easily fall victim to hayfever. 

Hayfever Seasons: The division of the year into three hayfever sea- 
sons does not apply at all strictly here. It is true that three seasons corre- 
sponding to those of the East may be recognized to some extent but a fourth 
in midsummer is added, due to the chenopods and amaranths which are here 
much more important than the ragweeds ; and in Arizona three of the false 
ragweeds, which are allergenically similar to the true ragweeds, flower early 
in spring, making really two ragweed seasons. Besides this, Bermuda 
grass, which is by far the most important hayfever grass if, indeed, not the 
most important of all causes of hayfever, throughout nearly the entire region, 
flowers at irregular and unpredictable intervals nearly all year round, for 
it depends much more upon rainfall and irrigation for its flowering than 
upon the cycle of the seasons. Also in western Texas the mountain cedar 
which is one of the most important causes of hayfever in this region, flowers 
in mid-winter. So, to speak of hayfever in the Southwest by seasons loses 
its meaning ; it is hayfever season all the time. 

The Trees 

Poplars. The commonest and most important of the poplars is the 
Arizona cottonwood (Populus McDougalii) growing naturally throughout 
much of the region and commonly planted in the irrigated valleys. Several 
other species are also common. The valley cottonwood (P. Wislizenii) is 
perhaps the best known tree of New Mexico where it is extensively used 
as a shade tree. It is also common in Arizona where it is counted as a cause 
of hayfever of secondary importance. The mountain cottonwood (P. angus- 
tifolia) is common in all the mountains of New Mexico and Arizona where 
it is regarded as a cause of hayfever of secondary importance. Rydberg's 
cottonwood (P. acuminata) grows in situations similar to those of the val- 
ley cottonwood. At Deming and Silver City in New Mexico it is used as 
a shade tree along with the valley cottonwood, and in both states it is 
regarded as a minor cause of hayfever. Besides the native species, the 
European white poplar (P. alba) is occasionally cultivated and is reported 
as a possible cause of hayfever at Williams and Flagstaff in Arizona and 
at Gallup in New Mexico. 

Ash. Among the ashes the Arizona ash (Fraxinus Toumeyi) is the 
commonest, particularly in the irrigated valleys of Arizona where it is 

Roger P. Wodehouse 190 Hay fever Plants 

believed to be of considerable importance in hayfever. The flowering ash 
(F. cuspidatd) also occurs in the region and is reported from Gallup, New 
Mexico, as a possible cause of hayfever. It flowers somewhat later, gen- 
erally in April. 

Oaks. More than twenty species of oak are recorded from the region, 
but for the most part they are not regarded as important in hayfever. A 
scrub oak (Quercus turbinella Greene) is believed to be of some importance 
in the mountainous parts of Arizona (PHILLIPS 1923), and other species, 
such as the bellota or black oak (Q. Emoryi Sarg.) and post oak (Q. sub- 
mollis Rydb.) are regarded by WATSON and KIBLER (1922) as of slight 

Junipers. The mountain cedar (Juniperus mexicana) in this region 
occurs only in part of Texas. In the region of Abilene it is said to be 
capable of causing hayfever from November to March (SELLERS 1934), 
though the bulk of its pollen is shed in December and January. Some half 
dozen other species occur in the region ; among them the one-seeded juniper 
(/. monosperma) is recorded as very abundant in Seligman, Winslow, 
Williams and Flagstaff in Arizona, and Gallup in New Mexico, where it is 
believed to cause some hayfever. The alligator-bark juniper (/. pocky- 
phlaea) also occurs abundantly almost throughout the entire region and is 
regarded as a possible cause of hayfever. These latter two species flower 
very early in spring but apparently not in midwinter as does the moun- 
tain cedar. 

Mesquite. Prosopis juliflora occurs principally in western Texas 
where it is said to be an important cause of hayfever (SELLERS 1929, 1934). 
It is also common in parts of southern New Mexico and Arizona. 

The Grasses 

Johnson Grass and Sorghums. Sorghum halepense is abundant in 
many localities, particularly in western Texas, but is of only local impor- 
tance in Arizona and New Mexico where it is said by PHILLIPS (1923) to 
affect only ranchers. Sorghum (S. vulgar e) and its variety Sudan grass 
(S. vulgar e sudanense) are cultivated, especially in western Texas where 
they may be minor contributors to hayfever. 

The Grama Grasses. Members of the genus Bouteloua are extremely 
common throughout the region. About ten species are counted, some of 
them constituting much of the original native range grass. The blue grama 
(B. gracilis), hairy or black grama (B. hirsuta), Rothrock's grama (B. 
Rothrockii) and six-weeks or needle grama (B. aristidoides Griseb.) are 
regarded by WATSON and KIBLER (1922) as of secondary importance, and 
the tall or sideoats grama (B. curtipendula) and purple grama (B. radicosa 
Griffiths) are reported as possible causes of hayfever in Arizona by LAM SON 
and WATRY (19336), and blue grama, hairy grama and six-weeks or mat 
grama (B. simplex Lag.) are reported as possible causes of hayfever at 
Williams, Arizona, by LAMSON and WATRY (1934). They all flower in 
the late summer after the rains but do not shed enough pollen to be of any 
real importance in hayfever in spite of the great abundance in which they 

Chapter IV 191 Regional Surveys 

Finger Grass. Chloris virgata, sometimes known as feather grass, a 
close relative of Bermuda grass, is regarded as of secondary importance in 
Arizona at higher elevations where Bermuda and Johnson grass do not 
grow. It flowers in late summer after the rains, but sheds so little pollen 
that it is relatively unimportant even though the plants may be numerous. 

Salt Grass. Distichlis spicata, since it is confined to the salt marshes 
and is a rather meagre pollen shedder, is of only local and minor importance. 
It is reported as a possible cause of hayfever at Winslow, Holbrook and 
elsewhere in Arizona. 

Bluegrass or June Grass. Poa pratensis, since it is extensively used 
for lawns wherever sufficient moisture can be maintained, may be an impor- 
tant cause of hayfever in some places. It is counted among the grasses of 
first importance in Tucson, Arizona (WATSON and KIBLER 1922), and its 
use as a lawn grass in Holbrook and Flagstaff, Arizona, is reported by 
LAMSON and WATRY (1933&, 1934). 

Brome Grasses. Members of the genus Bromus are particularly abun- 
dant in this region, the native perennial species forming a considerable 
portion of the forage in open woods of the mountain regions, but they all 
shed so little pollen that none is of much importance in hayfever. Downy- 
sheathed cheat or hairy chess (B. commutatus Schrad.), large mountain- 
brome (B. marginatus) and its variety the Great Basin brome (B. poly- 
anthus paniculatus Shear), and downy brome (B. tectorum) are recorded 
in great abundance and as possible causes of hayfever at Williams in Ari- 
zona (LAMSON and WATRY 1934). It is difficult, however, to judge their 
importance, but it is likely that they are deserving of some consideration in 
hayfever studies. 

Amaranths and Ghenopods 

Among the amaranths, the common pigweed is found in disturbed soils 
almost throughout the Southwest. The climate of this region is peculiarly 
favorable to its development, and as a result it appears to be more of a 
factor in hayfever than in most other regions. It is regarded by WATSON 
and KIBLER as of primary importance in Arizona, and is recorded by others 
in Phoenix, Flagstaff, Williams, Gallup and western Texas, where it is 
reported by SELLERS (1934) to be second in importance to careless weed 
(A. Pahneri). This latter species, though less widely distributed, appears 
to be much more important in regions where it does occur. It is stated by 
WATSON and KIBLER to be of primary importance in Arizona, and PHILLIPS 
reports that it is abundant throughout the Salt River valley in Arizona 
where besides being an invader of disturbed soils it is used in enormous 
quantity as a cover crop by citrus growers. 

Spiny Amaranth and western water-hemp occur in this region only in 
western Texas where they are regarded as among the weeds of primary 

Tumbleweed (Amaranthus graecizans L.) is a common weed in this 
region sometimes regarded as a cause of hayfever but is probably of little 
or no importance. 

Among the chenopods, lambsquarters occurs, as elsewhere, in consider- 

Roger P. Wodehouse 192 Hayfever Plants 

able abundance in disturbed soils and must be regarded as a secondary 
contributing factor. It is recorded in varying degrees of importance in 
Tucson, Phoenix, Flagstaff and Williams in Arizona, Gallup in New 
Mexico, and in western Texas. A related species (Chenopodium Watsoni 
A. Nels.) common in Arizona and New Mexico, is recorded as a possible 
cause of hayfever at Williams in Arizona. 

The saltbushes (A triplex) are abundant throughout most of the South- 
west. Wingscale (A. canesccns), generally known as shadscale, is among 
the most important hayfever plants of the region. Annual saltbush (A. 
Wrightii) is less widely distributed but is counted among the most important 
hayfever plants in southern Arizona. Other species such as A. lentiformis, 
A. poly car pa, the true shadscale (A. conjertijolia) and ribscale (A. Powcllii 
S. Wats.) are mostly confined to the desert regions, particularly in Arizona 
where they undoubtedly cause some hayfever. 

Russian Thistle. Salsola Pestifer is by far the most important member 
of this group. It is now found in great abundance in many places in the 
Southwest, often outranking the ragweeds. It is among the worst hayfever 
plants of western Texas and in northern Arizona and New Mexico. It is 
creeping into southern Arizona. "After six years of adaptation it has finally 
gained a foothold in the valley and is now rapidly spreading but is not yet 
important" (PHILLIPS 1923). 

Kochia. Being closely related to Russian thistle the kochias are simi- 
lar in appearance and habit and with pollen of similar allergenic properties. 
Two species are to be reckoned with ; the burning bush or Mexican fire bush 
(Kochia scoparia) occurs at Seligman, Holbrook, Winslow and to a certain 
extent at Gallup, while the redsage (K. amcricana) is reported to be working 
into New Mexico. Neither species, however, is yet important in the South- 

The Ambrosieae 

The ragweeds and their allies are represented by a large number of 
species but are much less important than in the East. The eastern short 
ragweed is occasionally found but hardly ever in considerable quantity. Its 
place is taken to a certain extent by western ragweed (Ambrosia psilo- 
stachya) which is abundant in southern Arizona, at Williams and at Flag- 
staff, but is in no way comparable with the short ragweed of the East. The 
eastern giant ragweed is not found in the region, but the western or Texas 
great ragweed (A. aptera) has a limited distribution in western Texas, 
parts of New Mexico and parts of Arizona, where it may occasionally be 
a severe local cause of hayfever. 

False Ragiveeds. The members of the genus Franseria are of much 
greater importance than the true ragweeds. Bur ragweed (F. acanthi- 
car pa) occurs almost throughout the region while the slender ragweed 
(F. tenuifolia) is more abundant in the southern part of Arizona and New 
Mexico. These two are the most important of the late-flowering franserias. 
Low ragweed (F. discolor) is of only local distribution in the plains of 
Arizona and New Mexico. The early-flowering franserias are considered 
to be more serious causes of hayfever than the late-flowering species. Rab- 

Chapter IV 193 Regional Surveys 

bit bush (F. deltoidea) is counted among the worst causes of early-summer 
hayfever but occurs only in Arizona, especially the southern part of the 
state. Canyon ragweed (F. ambrosioides) is limited to moist places in 
Arizona. Desert bursage or bush sandbur (F. dumosa) has only a limited 
distribution in desert plains of southwestern Arizona. 

The Marshelders. The genus Iva is represented by several species. 
Poverty weed (J. axillaris) is found, sometimes in great abundance, in alka- 
line soils almost throughout the region and is probably a local factor of 
secondary importance. 

Prairie ragweed (Cyclachacna xanthijolia) grows along streams and 
in waste places in New Mexico and is a common weed in cultivated fields 
in some parts of the state. Elsewhere in the region it appears to be of no 
importance though it occurs to a certain extent. Coarse ragweed (C. am- 
brosiaefolia B. & H.) occurs in dry mesas and sand hills throughout the 

Other members of the group which deserves attention are the grease- 
bush (Hymenoclca Salsola), occurring only in the southwestern part of 
Arizona, Jecote (//. monogyra) occurring in desert regions throughout, 
and two species of Dicoria, D. canescens occurring in the sandy deserts of 
southern Arizona and D. Brandegei in sandy soil in valleys of Arizona and 
New Mexico. Both are mentioned by WATSON and KIBLER as possible 
causes of hayfever in Arizona. 


Common Sagebrush. Artemisia tridentata is abundant in the northern 
part of the region, and is regarded as a cause of hayfever only in parts of 
northern Arizona and New Mexico. Gray sage (A. Wrightii) and its close 
relative, A. Carruthi Wood, are common in the canyons and meadows of 
the Upper Sonoran zone of the mountains of northern New Mexico. Sil- 
very wormwood (A. filifolia) occurs in the dry sandy plains and valleys of 
the Lower and Upper Sonoran zones almost throughout, and in the dry 
sandy valleys of New Mexico appears to occasionally cause a severe type 
of hayfever. 

The Common Sunflozvcr (Helianthns annnus), especially its variety, 
lenticularis ', grows in enormous quantity throughout much of this region 
and is probably occasionally a local cause of hayfever. 


A number of excellent botanical studies have been made of the hayfever situation 
of the Southwest. The earliest of these was the memorable work of WATSON and KIBLER 
(1922), reporting from Tucson, Arizona, done in association with Professor J. J. 
THORNBER of the University of Arizona. They find that the hayfever in Arizona lasts 
from about the end of January to the middle of November. They give a list of about 
a hundred plants capable of producing hayfever in the Southwest. 

At about the same time as this pioneer work of WATSON and KIBLER was pub- 
lished, appeared the study of E. W. PHILLIPS (1922), reporting from Phoenix, Arizona. 
He states that hayfever in central Arizona lasts about nine months of the year, and 
that much of the pollen which causes it comes from the weed flora of the irrigated dis- 
tricts which are not intensively cultivated, and that: "As population and irrigation in- 
crease so does the amount of pollen in the air and the number of those made ill by 
it". He reports the principal causes to be cottonwoods, principally Arizona cottonwood, 

Roger P. Wodehouse 194 Hayfever Plants 

Arizona ash, Bermuda grass, sorghum and several species of Atrlplex, careless weed, 
pigweed, bur ragweed (Franseria acanthicarpa) , rabbit bush and species of Artemisia. 

In a second paper PHILLIPS (1923) states that about 10 per cent of the population 
in central Arizona have hayfever, but no Indians and no Mexicans were found to be 
affected by it. Hayfever in the irrigated valleys is caused principally by Bermuda 
grass, to a lesser extent by Arizona cottonwood, Arizona ash, Johnson grass, careless- 
weed, wingscale and, to a slight extent, by rabbit bush. In the hill and mountain 
country hayfever is generally due to species of junipers, causing mild symptoms in late 
winter and early spring, scrub oak and cottonwoods producing only minor effects, Rus- 
sian thistle and wingscale which are the most important, and, in restricted areas of 
the northern part, bur ragweed and sagebrush, slender ragweed in the southern part, 
and in scattered localities western ragweed, field sagewort and gray sage. 

In a later paper PHILLIPS (1928) draws attention to the absence of eastern short 
ragweed but says that: "Persons who are primarily sensitized to the eastern ragweed 
always react more or less to the false ragweeds, western ragweed and rabbit bush, 
the strength of their reactions being usually in the order named". As a result of this 
cross sensitization, eastern ragweed cases usually have hayfever the first year of their 
arrival in Arizona. Such, however, is not true of eastern grass cases ; in Arizona they 
are nearly always free from hayfever for three to five years before they succumb to 
the effects of Bermuda grass pollen. 

PHILLIPS also draws attention to the changing character of the flora of Arizona. 
In speaking of slender ragweed (Franseria tenuifolia) he says: "This plant, always 
present in the Salt River Valley in scattered patches, has hitherto done no damage, so 
far as I know. But conditions are changing ; because of the city's rapid growth, con- 
siderable land that was formerly under clean cultivation has been taken over by real- 
estate developments and lies fallow. The false ragweed has moved onto the vacant lots. 
Last fall, stimulated by early rain, it pollinated freely enough to affect those sensitized 
to the ragweed group . . . The same is true of carelessweed". In a later note PHILLIPS 
(1930) states: "The area infested by this plant [slender ragweed] was much greater 
than in former years. There were found at the edges of the city, whole fields of it. 
Patches occurred along the roadsides, much as the true ragweed grows in the East". 
Russian thistle and western ragweed to a lesser extent at this time were observed to be 
invading the Salt River Valley. 

In a still later paper PHILLIPS (1932) summarizes his earlier work. He empha- 
sizes the fact that there are two ragweed seasons in Arizona. The first which lasts 
about a month, from March 10 until the hot weather sets in, is due to Franseria dumosa, 
F. deltoidea and F. ambrosioides and, in the southwestern part of the state, to Hymeno- 
clea Salsola. The second ragweed season, milder than the first, begins about the middle 
of September and lasts about six weeks, and is due to Franseria tennifolia. The worst 
of all hayfever plants, he finds to be Bermuda grass, which, he says, "Makes more 
trouble than all the rest combined". It is still possible, however, to escape hayfever 
in Arizona for "No one, whether from within or without the state, has pollen symptoms 
at the resorts located in the pines and remote from cultivation". 

WILSON (1934) reporting from Tucson, Arizona, on problems of hayfever of the 
Southwest, states that hayfever is particularly bad in the region not only because of 
the great abundance of atmospheric pollen, but also because of the drying effect that the 
desert atmosphere has on the mucous membranes, rendering them more than usually 
susceptible to the effects of pollen. In discussing WILSON'S paper both WATSON and 
KIBLER noted the spread of Russian thistle into Arizona within the past 12 years in 
sufficient quantity to become a real menace to hayfever sufferers. 

A valuable series of surveys of hayfever plants of the Southwest has been con- 
ducted by LAMSON in collaboration with ALVA WATRY. These papers are notable for 
their high botanical quality, and very excellent photographs of hayfever plants, taken 
both in the field and in the studio. The first of this series, A Botanical Survey of 
Needles, California (WATRY and LAMSON 1931) is considered in connection with our 
discussion of the hayfever plants of southern California (p. 197) so need not be discussed 
here though the material applies to this region to a certain extent because Needles is 
on the boundary between California and Arizona. Their second study deals with the 
anemophilous plants of Seligman, in central Arizona near Prescott. The authors fur- 

Chapter IV 195 Regional Surveys 

nish a list, with their times of flowering and relative abundance, of about 40 plants with 
hayfever possibilities. 

Another study by these authors (LAMSON and WATRY 19330) deals with the hay- 
fever plants of Winslow and Holbrook in the valley of the Little Colorado River in 
northern Arizona. The authors furnish pollen calendars of the anemophilous plants 
with hayfever possibilities. Hayfever there they find, is mainly caused by the pollen 
of grasses and chenopods, though Bermuda grass is nearly absent. 

LAMSON and WATRY (1934) in Survey of a Botanic Oasis in the Desert of 
Northern Arizona, discuss the hayfever plants of the San Franciscan Volcanic Field, at 
an elevation of 6500 to 7000 feet, including the towns of Flagstaff and Williams. They 
emphasize the localized distribution of the various species. For the most part hayfever 
plants are lacking, since the natural vegetation is of the montane forest type. The 
most important intruder appears to be Russian thistle. 

WATRY and LAMSON (1934) report a study of the hayfever situation at Gallup 
in the northwestern corner of New Mexico. The town is at an altitude of 6500 feet. 
The most abundant hayfever plants are Russian thistle, wingscale and sagebrush. Many 
grasses are abundant but these are mostly native species growing naturally so are un- 
important, and Bermuda grass is absent. 

The problem of hayfever in western Texas has been extensively studied by SELLERS, 
reporting from Abilene. This author, as already noted (p. 114) has repeatedly em- 
phasized the importance of mesquite in hayfever, and its abundance throughout a 
large part of Texas. SELLERS and ADAMSON (1932) find that the most important hay- 
fever plants in this region are members of the Chenopodiaceae and Amaranthaceae, more 
important than the ragweeds. SELLERS (1934, 1935) reports that in the west Texas 
area the grasses and Chenopodiales are the most important causes of spring and early- 
summer hayfever. 

VII. Southern California: 

Artemisia. HALL (SCHEPPEGRELL 1917a) states: "In California Arte- 
misia heterophylla and A. tridentata are the principal hayfever plants". It 
should, however, be pointed out that the latter species, though probably the 
most important hayfever plant of the Great Basin area, is in southern Califor- 
nia represented in quantity only on the desert slopes of the mountains ; west 
of the mountains where the country is most thickly populated it is scarcely 
known. A. heterophylla, on the other hand, grows almost throughout the 
region, scattered or in masses, often forming thickets on river banks or 
along ditches especially in low moist land. Also among species of first 
importance are A. calif arnica and A. dracunculoides. The former is par- 
ticularly abundant all along the coastal slope where it often forms dense 
masses, and the latter is abundant in the San Jacinto and San Bernardino 
Mountains, and locally at Los Angeles, but for the most part is not abun- 
dant enough in southern California to be of much importance in hayfever. 

Atriplex. The saltbushes in southern California are of relatively little 
importance west of the mountains. Wingscale, bractscale and lenscale 
occur abundantly in the Colorado desert and alkali interior where they are 
among the most important causes of hayfever. A. canescens, however, 
also occurs occasionally on the coastal slope in Ventura and San Diego 

Ambrosia pumila. The dwarf or Tia Juana ragweed "Inhabits Lower 
California and reaches its northern limit in southwestern San Diego County, 
California, where it may be a local factor" (ABRAMS 1932). 

Franseria. Of the false ragweeds HALL (SCHEPPEGRELL 1917a) points 
out that bur ragweed is abundant in the southern and eastern part of the 

Roger P. Wodehouse 


Hayfever Plants 

state, especially in sandy plains and fields. Slender ragweed also occurs in 
similar places but is much less common. The desert bur sage (F. dumosa) 
is found only in the hot dry deserts east of the mountains but in these re- 
gions it grows in great abundance. 















Juglans califomica (Calif, bl. walnut).. 






Quercus agrifolia (Coast live oak) 



Platanus orientalis (Oriental plane tree) 




Platanus racemosa (West, sycamore).. 



Populus Fremontii (Calif, cottonwood).. 



Cynodon Dactylon (Bermuda grass) 












Lolium perenne (Ryegrass) 







Phalaris minor (Canary grass) 



Avena fatua (Wild oat) 




Avena barbata (Wild oat) 






Lolium temulentum (Darnel) 




Poa pratensis (Kentucky bluegrass). . . . 






Sorghum halepense (Johnson grass) 







Dactylis glomerata (Orchard grass) 





Distichlis spicata (Salt grass) 








Bromus carinatus (Bromegrass) 





Bromus rigidus (Ripgutgrass) 




Plantago lanceolata (English plantain).. 






Amaranthus graecizans (Tumbleweed). . 








Amaranthus retroflexus (Pigweed) 








Atriplex canescens* (AVingscale) 






Atriplex bracteosa* (Bract scale) 







Atriplex rosea (Redscale) 





Atriplex argentea (Silverscale) 





Atriplex polycarpa (Allscale) 






Atriplex lentiformis* (Lenscale) .. . 






Chenopodium album (Lambsquarters).. 






1 1 1 

Salsola Pestifer (Russian thistle) 




Artemisia dracunculoides* (Dragon sage) 
Artemesia heterophylla* (Calif, mugwort) 
Artemisia califomica (Coast sagebrush) 









Artemisia biennis (Biennial wormwood) 








Artemisia tridentata* (Sagebrush) 





Ambrosia psilostachya (West, ragweed) 








Ambrosia pumila* (Dwarf ragweed) . . . 



Franseria acanthicarpa (Bur ragweed) . 







Franseria tenuifolia (Slender ragweed). 






Franseria dumosa* (Desert bur sage).. 






Hymenoclea Salsola* (Greasebush) 







Iva axillaris (Poverty weed) 

| | 








Xanthium pennsylvanicum (Cocklebur) 










Xanthium spinosum (Spiny clotbur) 








* Discussed in the accompanying paragraphs. 

Hymenoclea Salsola. Greasebush or Romerillo is chiefly of the des- 
erts where it is common on low hills and is regarded as among the most 
important hayfever plants (ABRAMS 1932). On the coastal slope it occurs 
only in northern Santa Barbara County and is probably of little or no 


The hayfever plants of southern California are exceptionally well known and their 
importance in hayfever understood largely because some of the world's leading botanists 

Chapter IV _197_ Regional Surveys 

happened to live in California and gave their whole-hearted cooperation with the local 
allergists in their hayfever studies. From cooperation of this kind arose the notable 
work "Hayfever Plants of California" (HALL 1922) in which all the species known to 
cause hayfever, and those with hayfever possibilities, throughout the state are listed 
with their times of flowering, their abundance and distribution within the state, to- 
gether with records of allergic reactions obtained with their pollen in the clinics of 
published by HALL forms the botanical foundation upon which most of the later in- 
vestigations have been based. HALL (SELFRIDCE 1918) also reports a survey of Califor- 
nia and Nevada, and, associated with Dr. SCHEPPEGRELL (SCHEPPEGRELL 1917a), con- 
tributes a comprehensive study of the role of the artemisias, marshelders, false rag- 
weeds and cockleburs of this region. To the same author (HALL 1917) we are also in- 
debted for a study of the relation of farm weeds of the region to hayfever, and for the 
first definite proof (HALL 1918) that California black walnut pollen is a serious cause 
of hayfever throughout much of southern California. 

A notable contribution of similar kind is "The Hayfever Plants of the Western 
States" (ABRAMS 1932). This study covers the area from California east to Texas 
and north to Oregon, but Part I, all that is so far published, treats only members of 
the Ambrosieae. PINESS, MILLER and McMiNN (1926) in their botanical survey of 
southern California give a list with pollinating dates, of all the known hayfever plants 
and those with hayfever possibilities. The very valuable table from this work has been 
reprinted by VAUGHAN (1931). PINESS (1925), PINESS and McMiNN (1927) fur- 
nish a comprehensive study of the pollens of the most important hayfever plants of 
California, illustrated by photomicrographs and drawings of the pollen grains, and with 
a key for their identification. 

Intensive local studies of several regions have also been made. PINESS and MILLER 
(1930) made detailed studies of two isolated communities, one a mining community the 
other a potash community, both in desert conditions and with an unusually high pollen 
incidence. They found that the great majority of people in these communities began 
to have hayfever only after one to four years residence there. In the mining commu- 
nity the principal causes of hayfever were found to be Bermuda grass, Russian thistle, 
wingscale and redscale, while in the potash community the principal cause was Bermuda 
grass. He says that the high general incidence of hayfever in these communities, taken 
in consideration with the low general incidence of positive heredity among the inhabit- 
ants, suggests the possibility that even so-called nonallergic individuals may become 
sensitized by a super-abundance of pollen. 

WATRY and LAMSON (1931) in "A Botanical Survey of Needles, California" point 
out that in and about Needles, since it is situated on the Colorado River, the vegetation 
departs widely in character from that of the surrounding desert. The real causes of 
hayfever in Needles are found to be Bermuda grass, growing between the dyke and the 
river and in lawns, and the three species of saltbush, Airiplex lentijormis, A. polycarpa 
and A. elegans. Other plants of the region of less but still considerable importance, are 
willow (Salix nigra) and poplar (Populus Fremontii} flowering in February, and the 
desert bur-sage (Franseria dumosa}, and Hymenoclea Salsola later in the season. But 
there is, at present, no Russian thistle nor wingscale. 

STEALY (1936) contributes a two-and-a-half year study of the pollen situation in 
San Diego, giving records of atmospheric pollen together with their relation to wind 
velocity and rain fall. He finds that pollen allergy at San Diego is a perennial disorder, 
but the amount of pollen varies from year to year depending principally upon rain fall. 
The principal sources of pollen he finds to be the ragweeds, false ragweeds, chenopods, 
amaranths and grasses. 

VIII. The North Pacific States (Northern California, Nevada, 
Oregon, Washington) : 

Acacia. Many Australian species of acacia have been introduced into 
this region and are extensively used as shade trees in streets and parks in 
the towns and cities of California; they are especially abundant in San 

Roger P. Wodehouse 


Hayfever Plants 

(Northern California, Nevada, Oregon, Washington) 






















Acer Negundo (Boxelder) 




Acer* (Maples) 




Alnus* (Alders) 





Betula* (Birches) 




Corylus californica (California hazel) . . . 
Juglans californica* (Calif, bl. walnut) 
Platanus acerifolia (London planetree) . 

Populus* (Cottonwoods) 
Salix sitchensis (Sitka willow) 
Salix* (Willows) 









Quercus Douglasii (Blue oak) 



Quercus agrifolia (Coast liveoak) 



Quercus Wislizenii (Interior liveoak) . . . 
Quercus* (Oaks) 

i ii 




Kucalyptus* (Gumtrees) 

i ii 






Olea europaea (Olive) 



Ligustrum (Privets) 



Fraxinus* (Ashes) .... ... 




Chamaecyparis Lawsoniana* (Cypress).. 
Schinus molle (Pepper tree) 





Garrya elliptica* (Silk-tassel bush) 
Morus (Mulberry) 







Agrostis alba (Redtop) 






Avena fatua (Wild oat) 







Avena barbata (Wild oat) 






Bromus carinatus (California brome) . . . 
Bromus hordeaceus (Soft cheat) 
Bromus rigidus (Ripgut grass) 
Bromus (Brome grasses) 







Cynodon Dactylon (Bermuda grass) 
Dactylis glomerata (Orchard grass) 
Distichlis spicata (Saltgrass) 
Hordeum murinum (Mouse barley) 
Lolium perenne (Perennial ryegrass).. 
Lolium temulentum (Darnel) 
Lolium multiflorum (Italian ryegrass).. 
Holcus lanatus (Velvet grass) 





















Phalaris californica (Canary grass) 
Poa annua (Low spear-grass) 
Poa compressa (Canada bluegrass) 
Poa pratensis ( Junegrass) 


















Ammophila arenaria (Beach grass) 
Sorghum halepense (Johnsongrass) 

Festuca (Fescue grasses) . 










Anthoxanth. odorat. (Sw. vernalgrass) . . 
Phleum pratense (Timothy) 





Koeleria cristata (Western Junegrass).. 
Agropyron Smi-thii (Bluestem) 






Agropyron repens (Quack grass) 





Amaranthus retroflexus (Pigweed) 
Amaranthus graecizans (Tumbleweed) 
Atriplex rosea (Red orach) 







Atriplex canescens* ( Wingscale) 
Atriplex* (Saltbushes) 










Chenopodium album (Lambsquarters) .. 
Chenopodium ambrosioides (Mex. tea).. 
Salicornia ambigua* (Pickleweed) 
Salsola Pestifer* (Russian thistle) 
Plantago lanceolata (English plantain). 
















* Discussed in the accompanying paragraphs. 

Chapter IV 


Regional Surveys 

Table VllL Concluded: 




o 1 



> g> 







> ^ 





Rumex Acetosella (Sorrel dock) 
Rumex* (Docks) 






i! i 


Amb. psilostachya (West, ragweed) 


II II 1 

1 Illl 



Franseria bipinnatifida* (Beach sandbur) 
Franseria Chamissonis* (False ragweed) 
Franseria acanthicarpa* (Bur ragweed) . . 






II II 1 






Franseria tenuifola* (Slender ragweed).. 




Iva axillaris (Poverty weed) 






u u 

1 1 

Cyclachaena xanthifolia* (Burweed) 

1 1 






Xanthium spinosum (Spiny clotbur) .... 





1 Illl 

Xanthium (Cockleburs) 



ii ii 

I Illl 

Artemisia californica (Coast sagebrush) 


u u 

1 Illl 


Artemisia heterophylla (Mugwort) ... . 

ii ii 


I || 

Artemisia tridentata* (Sagebrush) 


u in 

1 III 





Artemisia dracunculoides (Dragon sage) 




Artemisia biennis (Biennial wormwood) 


u i 



Artemisia ludoviciana (Prairie sage)... 


u i 


Taraxacum officinale (Dandelion) 





u HI 


* Discussed in the accompanying paragraphs. 

Francisco. Though insect pollinated, it is suspected that their pollen is 
capable of causing hayfever. In hayfever studies the different species are 
rarely differentiated. ROWE (1932), however, mentions Acacia melano- 
carpa as a common species in San Joaquin County, California. Native 
species do not occur. 

Maples. Besides boxelder, which is widely distributed in this region 
along stream bottoms and occasionally planted as a shade tree, the silver 
maple (Acer saccharinum) and sugar maple (A. sacchamm) are planted in 
city streets. Oregon or Big-leaf maple occurs rather abundantly in the 
valleys and protected coast region of northern California (RowE and HOWE 
1935) and northward. But no maple appears to be of importance in 

Alders. Besides the white alder (Alnus rhombifolia) , which is per- 
haps the commonest in California, red alder (A. rubra) is recorded for 
California, and thin-leaved alder (A. tenuijolia) and Oregon alder (A. ore- 
gona) are recorded for western Oregon and Washington. 

Birches. White birch, both in its natural form (Betula alba) and the 
weeping form (B. alba laciniata pendula) are planted in city streets and 
parks. In eastern Oregon and Washington the spring birch (B. fontinalis) 
is reported to be the common species. 

Walnuts. Besides the native species, Juglans californica and /. Hindsii 
which are known to be important causes of hayfever in California, the 
eastern black walnut (/. nigra) and the English walnut (/. regia) are 
extensively planted and are regarded by ROWE (1928, 1929, 1932) as con- 
tributory causes of hayfever. 

Roger P. Wodehouse __200 Hayfever Plants 

Cottonwoods. Several species of Populus are common in the region. 
In California P. deltoides and P. Fremontii are regarded as probable causes 
of hayfever. These and other species flower in California mostly in March 
and early April. In Oregon and Washington P. tremuloides and P. tricho- 
carpa are recorded as causes of hayfever in April and May. 

Willows. Many species of Salix occur in the region ; the arroyo 
willow (S. lasiolepis) , sitka willow (S. sitchensis), red willow (S. laevi- 
gata) and dune willow (S. Pipcria) are recorded as possible causes of hay- 
fever in various parts of the region, but none is believed to be important. 

Oaks. Quercus is represented by many species. The coast live oak 
(Q. agrijolia), interior live oak (Q. Wislizenii), valley oak (Q. lobata 
Nee), scrub oak (Q. dumosa), blue oak (Q. Donylasii Hook. & Arn.) and 
others are common in California, while Oregon oak (Q. Garryana) and 
California black oak (Q. Kellogii Newb.) are common in Washington and 

Eucalyptus. Several species of gum tree are extensively cultivated in 
California. Though the trees are primarily insect pollinated, the pollen has 
been recorded in the air by DEAMER and McMiNN (1935). 

Ash. Oregon ash (Fraxinus oregona) is common throughout much 
of the region, and the European flowering ash (F. Ornus) and Arizona 
ash (F. velutina) are planted as street and roadside trees, flowering in 
February and March in California and about April in Washington and 

Elms. Though no elms occur naturally on the Pacific coast, ROWE 
(193?) records the European elm (Uhnus proccrd), in several varieties, 
and other species planted along streets and in parks in central California. 

Lazvson Cypress. Chamaccyparis Lawsoniana occurs naturally 
throughout much of the region and it and the related cypresses (Cuprcssus) 
and junipers are planted as street and park trees. 

Saltbushes. Many species of Atriplex occur in the region. Perhaps 
the most abundant is A. patula, including its variety hastata. This is re- 
garded by ROWE (1928) as among the most important plants of the San 
Francisco Bay region, based upon the skin reactions obtained with its pollen. 
It is, however, restricted to the salt marshes, principally along the coast. 
Red orache is counted by ROWE (1932) among the most important plants 
of San Joaquin County, California. A. coronata, A. leucophylla, A. semi- 
baccata and other species are probably of some importance in California. 
A. canescens is recorded among the most important hayfever plants of 
Nevada (ALBERT and DEBELL 1927) but not elsewhere in the region. 

Pickleweed. Salicornia ambigua occurs only in salt marshes princi- 
pally along the coast. 

Russian Thistle. Salsola Pestijer is extremely abundant east of the 
mountains. It is regarded as the most important hayfever plant of Nevada 
(ALBERT and DEBELL 1927) and is also of the utmost importance in eastern 
California, Oregon and Washington, and is regarded by ROWE (1932) as 
among the most important plants of San Joaquin County, California, grow- 
ing on "alkaline sand, roadsides and grain fields", but it does not occur to 
any extent elsewhere along the coast. 

Chapter IV _201 Regional Surveys 

Docks. Besides the sorrel dock which occurs throughout the region, 
curly dock (Rumex crispus) is likewise widely distributed. Western dock 
(R. occidentalis) , green dock (R. conglomerate) and fiddle dock (R. 
pulcher) are abundant in California (RowE and HOWE 1935). 

Western Ragweed. Ambrosia psilostachya is important throughout 
most of the region but is absent from western Oregon and western Wash- 

False Ragweeds. Franseria bipinnatifida and F. Chamissonis occur 
principally along the sea shore, while F. tenuifolia and F. acanthicarpa occur 
in the eastern part of the region. 

Marshelders. Iva axillaris and Cyclachaena xanthijolia are impor- 
tant only in the eastern part of the region. 

Sagebrushes and Mug worts. Artemisia pycnocephala occurs only on 
the sand dunes of the sea shore. Common sagebrush is among the most 
important hayfever plants in the eastern part of the region, especially 
eastern Oregon and eastern Washington, but does not occur to any extent 
west of the mountains. Budbrush (A. spinescens) is especially common in 
Nevada where it appears to be of some importance in hayfever. 

Sunflower. Helianthus annuus, both wild and cultivated, is extremely 
abundant throughout much of the region. ROWE (1932) reports 1000 
acres in San Joaquin County, California, devoted to its culture. Though 
insect pollinated it is probably a local factor of some importance. 

Pepper Tree. Schinus Molle L. is cultivated in parts of California and 
is suspected of being a local cause of hayfever. Of it SCHEPPEGRELL (1925) 
states that it is reported by Professor GEORGE POTTS of the Department of 
Botany, Greys University College, Bloemfontein, South Africa, to be a 
severe cause of hayfever in Bloemfontein, Kimberley and other towns of 
South Africa where it is extensively cultivated. This was proved by catch- 
ing the pollen on atmospheric pollen plates when the trees were flowering, 
and by cutaneous tests with the pollen on patients afflicted with hayfever 
at the same time. The tree is native of tropical America and belongs to 
the Anacardiaceae or Sumac family. 


The earliest published contribution to our knowledge of the hayfever situation in 
this region, as far as I know, is that of SCHEPPEGRELL (1917a), done in association with 
Professor H. M. HALL. Though this paper is now twenty-seven years old it is still 
of great value for its excellent descriptions and illustrations of hayfever plants, and 
accurate estimates of the importance of their pollen in hayfever. 

SEWRIDGE (1918) published in his paper on hayfever in California an excellent 
botanical survey of California and Nevada by H. M. HALL, in which all the plants 
known to cause hayfever and those with hayfever possibilities are listed in their biolog- 
ical classification. SELFRIDGE (1919) listed fifteen species of hayfever plants with 
which he considered it necessary to test hayfever patients for pollen sensitization in 
San Francisco, recording the number of reactions he got from the pollen of each with 
a selected group of cases. Broncho grass and wild oat head the list, with salt grass, 
canary grass, June grass and wheat not far behind. Plantain, mugworts, poverty weed 
and sagebrush also gave a fair proportion of reactions. The spring type of hayfever, 
due to grasses, he found to predominate in this part of California. The same author 
(SELFRIDGE 1920) extended his list of necessary pollens to include southern California, 

Roger P. Wodehouse 202 Hayfever Plants 

taking care to emphasize the necessity of using only those of such species as are found 
locally and the futility of employing those of related species from the East, the only 
ones which the eastern commercial firms were able to supply at that time. Of some 
interest is his record of "My discovery that the pollen of ray grass (Lolium perenne) 
is perhaps the most important hayfever producer of all the grass family found on the 
Pacific Coast". This grass had been omitted from his earlier list even though its 
primary importance in California, Washington and Oregon had already been pointed 
out by SCHEPPEGRELL (1917a). 

HALL (1922) summarized and extended his work already done in association with 
SCHEPPEGRELL and SELFRIDGE in his catalogue of hayfever plants of California. This 
work includes 175 species of plants with proved or possible hayfever potentialities and 
15 others which he points out are frequently but erroneously regarded as causes of 
hayfever. The relative importance of each of the others is indicated; "determined by 
field observations as to the abundance of the plants, by the amount and size of the 
pollen produced, and by reports as to the frequency and extent to which positive results 
have been obtained with the extracts". In determining the first two of these criteria 
HALL drew upon his extraordinary powers of observation and his superb knowledge 
of Western botany ; in the third criterion he had the able assistance of such outstanding 
The result of this has been that the catalogue stands as valuable today as a general 
survey of California as when it was written, for so complete and meticulously accur- 
ate was HALL'S work that little can ever be added to it or taken from it, except as the 
flora changes through the destructive activities of human incursions. But, as HALL 
points out, "hayfever of this region is very much a local problem; a species of first rank 
in one district may be of minor significance in another, and vice versa". To offset this 
to a certain extent he furnished supplementary district lists for the San Francisco Bay 
Communities, Sacramento and San Joaquin Valleys, and Los Angeles-Pasadena dis- 
trict. The road to further development of our knowledge of the hayfever botany of 
this region from this time on has lain almost entirely in the study of the hayfever con- 
ditions of more and smaller districts. 

A series of such studies was instituted by ROWE (1928). In his first paper he 
records the result of a botanical survey and atmospheric pollen counts of the east shore 
of San Francisco Bay. The botanical survey presents a list of all the plants known to 
cause hayfever and those with hayfever possibilities, together with their relative abun- 
dance in the various communities of the district, and their times of flowering. The at- 
mospheric pollen records show that pollen is found in the air throughout the year, the 
least occurring in August and September. 

ROWE (1929) furnishes a botanical survey of San Francisco, giving a list of all 
the plants of the district known to cause hayfever or with hayfever possibilities, show- 
ing their flowering periods and relative abundance in the different parts of the district. 
He points out that certain differences exist between this district and that of the east 
shore of San Francisco Bay. Bromus maritimus, Franseria Chamissonis, and Artemisia 
pycnocephala are common enough to be taken into definite account in treating patients 
who live in San Francisco, while these plants are absent from the east shore of San 
Francisco Bay. Golden Gate Park with its large numbers of such trees as acacia, oak, 
birch, sycamore and an abundance of grasses, is a source of much pollen which is car- 
ried to the residential districts of the city. 

ROWE (1932) presents a botanical survey of San Joaquin County in central Cali- 
fornia, conducted by Professor E. E. STANFORD. A list is furnished including "that 
portion of its flora which produces or may possibly produce pollen sensitization," and 
giving the relative importance, abundance, dates of flowering and distribution within 
the district of the various species. He finds marked differences between the flora of 
this district and those of the two previous reports. The San Joaquin area, especially 
the irrigated section is characterized by an abundance of Amaranthaccae and Chenopo- 
diaceae, including such notable hayfever plants as Russian thistle and species of Atri- 
plex. These floristic differences he finds to be decidedly reflected in the character 
of the hayfever most frequently encountered : "Patients from San Joaquin County 
usually give large reactions to amaranth, chenopod, Atriplex and Salsola kali [Russian 

Chapter IV 203 Regional Surveys 

thistle] pollens, whereas reactions to the Artemisia pollens, with or without reactions 
to the foregoing chenopod pollens are the rule in patients living in the Bay counties". 

ROWE and HOWK (1935) report a botanical survey of northwestern California, 
dealing with the regions west of the Klamath Mountains, including the counties Del 
Norte, Humboldt, Trinity, Mendocino, Lake and Sonoma. A list is furnished of ane- 
mophilous plants with their dates of flowering and relative abundance. The grasses 
produce most of their pollen in late spring (May) and through the summer to the end 
of July. Along the coast in the north the silk-tassel bush (Garrya elliptica Dougl.) is 
commonly found. The most important regions from the view-point of the number 
of hayfever-producing plants are the Humbolt Bay littoral, the Russian River Valley 
and the plains about Clear Lake. 

DEAMER, JENKINS and LAZARUS (1938) report a pollen survey on the Arcata dis- 
trict, Humbolt County. They find the pollinating season for grasses unusually long, 
extending from April to November, and the pollen of ragweed more abundant than in 
the San Francisco area. On their slides they encountered the pollens of grasses, 
ragweed, sagebrush, amaranth, chenopod, plantain, dock, nettle, alder, cypress, pine, 
cottonwood, willow, elm. 

The botanical aspect of the hayfever situation in Oregon has been studied by 
CHAMBERLAIN (1927), listing the most important plants with the dates of their pollina- 
tion. The state is divided from north to south by the Cascade mountains. East of the 
mountains is an elevated plateau with a relatively dry climate and much wind, condu- 
cive to anemophilous pollination. Most of the hayfever of this region is caused by 
grasses, species of Atrifilex, Russian thistle and the artemisias. The western part of 
the state comprises several river valleys presenting various types of flora. The largest 
of these is the Williamette valley in which is located the city of Portland. The author 
finds that : "Approximately 95 per cent of all hayfever in Oregon is of the early or mid- 
summer type, caused by the pollens of the grasses". Forty-five per cent of the cases in 
one group were found to be sensitive to the pollens of trees and 60 per cent to the 
pollen of late-flowering weeds. 

STIER, HOLLISTER and BONSER (1930) report a botanical survey of the hayfever- 
producing plants of Oregon and Washington. This report also includes the states, 
Idaho, Montana, Wyoming, Utah and Colorado, is referred to again in the discus- 
sion of these states. The authors furnish a list of anemophilous plants, and others, 
with hayfever possibilities, giving their relative abundance in the eastern and western 
parts of Oregon and Washington, and the life zones or elevations at which they are 
characteristically found. Russian thistle is found to occur principally east of the moun- 

The hayfever flora of western Oregon and Washington these authors report to 
be quite different. The most important factor appears to be velvet grass. Timothy, 
orchard grass, ray grass, Italian rye grass, Kentucky blue grass, brome grasses, and 
plantain are also common and important contributors to hayfever during early summer. 
The authors also find that the common dandelion grows in enormous abundance and 
to unusual size and believe it to be an important factor in hayfever, even though it is 
insect pollinated. 

SCHONWALD (1937) presents a pollen calendar for western Washington, and curves 
for the atmospheric pollen of the principal species. In the vicinity of Seattle he finds 
no ragweed, artemisia or Russian thistle. The principal causes of hayfever he finds 
to be hazel, alder, birch, poplar, maple and elm among the trees, and June grass, or- 
chard grass, ray grass, velvet grass and plantain among the grasses and weeds. This 
author also finds that the common bracken fern (Pteris aquilina L.) is exceedingly 
common, and its spores are caught in large numbers on his pollen slides from July to 
September. Also many hayfever patients exhibit sensitivity to bracken spores and 
respond favorably to treatment with their extract. 

STROH (1940) has recently furnished a pollen survey of Seattle and vicinity. He 
finds that tree hayfever occurs from February 1 to March 15 and is mostly due to the 
pollen of alder and birches which latter flower in April. Grass hayfever he finds to 
occur from April to mid June. Weed hayfever which occurs in the latter part of the 
summer, he finds to be of little importance, caused mainly by the pollen of goosefoot. 

Roger P. Wodehouse _204 Hayfever Plants 

pigweed and mugworts. He reports that, though ferns are common in the region, they 
cause no symptoms of hayfever. 

Of special interest in this connection is the work of PIEMEISEL and LAWSON (1937) 
on the types of vegetation in the San Joaquin valley. This study was made to determine 
the effect of the surrounding vegetation on the curly-top disease affecting such plants 
as beets, tomatoes, melons, squash and other important crop and ornamental plants. 
The authors furnish detailed maps showing the distribution of the various types of 
vegetation, both before its occupation by white settlers and in its present condition. 
"The San Joaquin Valley", they say "is a meeting place of the desert formations of the 
interior, the Mohave and Colorad'o deserts, and the grassland and broad sclerophyll 
formations of the Pacific slope". The plant formations as originally occurring were 
tree savanna, consisting of a scattered growth of oak trees and an undergrowth of 
perennial grasses, Pacific grassland, originally consisting of grasses 'as the native 
perennial bunchgrasses and the relatively harmless native plains grasses, desert salt- 
brush formation, consisting chiefly of A triplex poly car pa and other species of Atriple.v, 
and the lowland types of vegetation, consisting principally of such plants as seepweed 
(Dondia Moquini), alkali heath and salt grass, and in the wetter situations, pickle- 
weed. But owing to improper agricultural use of much of the land the original 
flora has given way to native and introduced weeds which serve as intermediate hosts 
for the insect vectors of the plant virus diseases. Among these are included such notable 
causes of hayfever as Russian thistle, wild oat, red brome, slender fescue, mouse barley, 
Australian saltbush, bract scale and fogweed. The authors close their discussion with 
these words : "The correction of two uneconomical practices, intermittent farming 
and destructive grazing, is in accordance with the general principles of land conserva- 
tion. Such a correction would also result in greatly reducing the leaf hopper popula- 
tion and the curly top damage to the crops". And to this one may also add, much of 
the late-summer type of hayfever. 

IX. The Rocky Mountain States (Idaho, Montana, Wyoming, Utah, 
Colorado) : 

In the main the hayfever of the region falls into three seasons as in the 
East. The first, of relatively slight importance, lasts from March to May, 
and is due principally to the cottonwoods or poplars, boxelder and birch. 
The second season, accounting for possibly one third of the cases, begins 
early in May and continues into July, and is due to the grasses, principally 
the introduced agricultural species such as timothy, redtop, orchard grass, 
June grass, the fescues and wheat grasses. Bermuda grass is not a factor, 
though it has been reported to occur in some parts of this region. The 
third season accounting for about 75 per cent of the hayfever, begins about 
July the first and continues until October, and is due to Russian thistle, 
sagebrush and other artemisias, amaranths and chenopods, with the rag- 
weeds, false ragweeds and prairie ragweed playing a minor role, and this 
only locally. The short and tall ragweeds are abundant enough to be im- 
portant in the extreme eastern part of the region and the short in part of 
Utah, but elsewhere neither they nor other members of the ragweed tribe 
are important causes of hayfever. 


Junipers. Juniperus utahensis occurs in the Upper Sonoran zone 
throughout much of the region flowering in April (TEMPLETON 1924). 
/. monosperma and /. scopulorum are recorded from the region of Pikes 
Peak and Colorado Springs (SERVICE 1934). 

Chapter IV 


Regional Surveys 

Poplars and Cottonwoods. Western or river cottonwood (Populus 
Sargentii), willow-leaf cottonwood (P. angustifolia) , Rydberg's cotton- 
wood (P. acuminata) and the trembling aspen (P. tremuloides) are the 

(Idaho, Montana, Wyoming, Utah, Colorado) 











^ c 

3 ^ 

1 ^ 




Juniperus* (Junipers) 




Betula fontinalis (Mountain birch) . . . 



Alnus tenuifolia (River alder) 



Populus Sargentii (Western cottonwood) 

Populus* (Cottonwoods) 




Salix (Willows) 



Acer Negundo* (Boxelder) 




Acer* (Maples) 




Quercus Garnbellii (Scrub oak) 


Quercus Gunnisonii (Scrub oak) 


I 1 ! 1 

Taraxacum officinale (Dandelion) 
Phleum pratense (Timothy) 




Agrostis alba (Redtop) . 



|| || 

Koeleria cristata (Western Junegrass) . . 
Distichlis spicata (Saltgrass) 
Dactylis glomerata (Orchard grass) 





II 11 

Poa prat ens is (June grass) 




Poa compressa (Canada bluegrass) 


Illl II 

Festuca elatior (Meadow fescue) 





Bromus* (Brome grasses) 


Agropyron* (^^heat grasses) 



Illl II 

Hordeum jubatum* (Foxtail barley) 
Elymus condensatus (Giant wild rye) .. 
Plantago lanceolata (English plantain).. 
Rumex Acetosella (Sorrel dock) 
Chenopodium album (Lambsquarters).. 
Chenopodium glaucum (Goosefoot) 
Allenrolfia occidentalis (Burroweed) 
Kochia scoparia* (Burning bush) 




Illl II 

Illl II 

"i: i! 

ill SI 


II Illl 
II Illl 




Illl II 


Atriplex* (Saltbushes) 


Illl II 



Sarcobatus vermiculatus (Greasewood) . . 
Salsola Pestifer (Russian thistle) 
Amaranthus retroflexus (Pigweed) .... 
Acnida tamarisc.* (West, waterhemp).. 
Tva axillaris* (Poverty weed) 
Cyclachaena xanthifolia (Burweed) 
Ambrosia trifida* (Tall ragweed) 
Ambrosia elatior* (Short ragweed) 
Amb. psilostach.* (West, ragweed 
Franseria acanthicarpa* (Bur ragweed) 
Artemisia tridentata (Sagebrush) 
Artemisia ludoviciana* (Green sage) 
Artemisia frigida (Pasture sage) 




Illl II 

ill! :i 

mi i 


1 III 
1 III 
II 1 


1 Illl 

1 III! 

II Illl 



II Illl 

Xanthium pennsylvanicum (Cocklebur) 

ii i 

II Illl 

* Discussed in the accompanying paragraphs. 

common native cottonwoods of the region. Such introduced species as the 
European white poplar, Carolina cottonwood (P. Eugenei) and the Lom- 
bardy poplar are planted in the parks and city streets. The cottonwoods 
on account of their abundance and the enormous quantities of pollen that 

Roger P. Wodehouse 206 Hayfever Plants 

most of them produce are probably among the most important trees of 
the region. 

Maples. The most important species of maple is the boxelder ; it is 
reported to be the commonest tree in Salt Lake City and among those of 
first rank in the region of Pikes Peak and Colorado Springs. The moun- 
tain maple (Acer grandidentatmn Nutt.) occurs naturally in canyons 
throughout much of the region, and silver maple (A. saccharinum) is 
planted in city parks and streets. Both species flower in March and April 
and probably contribute to some extent to the hayfever. 


Brome Grasses. Three species of brome grass, Browns hordeaceous, 
B. tectorum and B. secalinus are common in the region and are generally 
reported in hayfever surveys, but it is unlikely that they are of any impor- 
tance on account of the small amount of pollen that they shed. 

Wheat-grasses. At least seven species of wheat-grass arc common in 
the region and contribute to some extent to the production of hayfever. 
Bluestem (Agropyron Smithii), flowering from June to August, is abundant 
in the Upper Sonoran and Transition Zones. Thick-spike wheat-grass 
(A. dasystachynm Scribn.) is reported to be important in Salt Lake City 
and Colorado Springs. Wheat-grass (A. pseudorcpens Scribn. & Smith) 
and slender wheat-grass (A. paitciflorum Hitch.) are reported for parts of 
Utah. Bluebunch wheat-grass (A. spicatum Scribn. & Smith) and Great 
Basin wheat-grass (A. inerme Rydb.) are abundant throughout much of 
the region, especially in Utah and to a certain extent in western Colorado. 
Quack grass (A. re pens) occurs at various places but is less abundant than 
the other species and appears to be of no importance. 

Foxtail Barley. Hordeum jubatum and meadow barley (H. nodosum 
L.) are widely distributed in this region, and mousear barley (H. murinmn} 
occurs in Idaho and Utah and are probably minor contributing causes of 
early-summer hayfever. 

Other species which probably contribute to a certain extent to early- 
summer hayfever are the little meadow or short-awned foxtail (Alopccurns 
aequalis Sobol. or A. aristulatus Michx.) growing in water or w^et places 
in the Transition Zone almost throughout the region, blue wild-rye (Elymns 
glaucus Buckl.) occurring in meadows of the Transition Zone, brook grass 
(Catabrosa aqnatica Beauv.) growing in mountain meadows around springs 
and along streams in Utah (BARRETT 1934), knot grass (Paspalum dis- 
tichum L.) growing in ditches and recorded in the region of Pikes Peak 
and Colorado Springs (SERVICE 1934), and the mat grama (Boittcloua sim- 
plex Lag., B. procumbens Griffiths) growing in sandy plains. 


Burrozveed. Allenrolfia occidentalis is recorded by ANDERSON (1930) 
for parts of Utah. Elsewhere it appears to be unimportant or absent. 

Burning Bush. Kochia scoparia is believed to be the most important 
cause of hayfever throughout most of the inhabited parts of Colorado. Out- 

Chapter IV 207 Regional Surveys 

side of the state, however, it appears to be unimportant or absent, though 
it is recorded for parts of Utah. 

Saltbushes. Besides Atrlplcx canescens, are reported A. rosea, A. 
hortcnsis, A. hastata, A. argentea, A. truncata and A. confcrtifolia as pos- 
sible contributory causes of hayfever. 

Amaranths. Pigweed is so abundant in weedy places almost through- 
out the region that it appears to be a factor of considerable importance in 
hayfever. Its close relatives Amaranthus blitoidcs, A. pahncri, and A. 
graccizans also occur and are reported as important local causes of hayfever. 

Acnida. Western water-hemp has only a limited distribution in the 
region, but is reported by WARING (1925, 1926) to be important in the 
vicinity of Denver, and by SERVICE (1934) in the vicinity of Pikes Peak 
and Colorado Springs. 

Ragiveeds. The tall, short and western ragweeds occur in this region. 
Of these only the short is of much importance. In parts of Utah it is con- 
sidered important by ANDERSON (1930) and is given a third place rating 
by BARRETT (1934). In the regions of Denver, Pikes Peak and Colorado 
Springs both the tall and short species occur commonly along roadsides and 
in waste places but are generally considered less important than Russian 
thistle and the sagebrushes. Both also occur in the extreme eastern sections 
of Montana and Wyoming. Western ragweed is still less important though 
it occurs rather abundantly in about the same parts of the region as the 
other two species and in Utah. 

False Ragweeds. Besides the bur ragweed which occurs in the Sono- 
ran and Submontane Zones throughout much of the region, the slender 
ragweed (Franscria tennifolia) occurs in the Sonoran Zone and is reported 
(BARRETT 1934) as important in Utah. 

SagebrusJics and Mugivorts. The common sagebrush is among the 
worst causes of hayfever in most parts of this region, but it is absent from 
central and western Montana and western Idaho. Green sage (A. ludovi- 
ciana) occurs in about the same parts of the region also in western Montana 
and northern Idaho but is less abundant and less important. Pasture sage 
(A. jrigida) occurs in the Sonoran Zone almost throughout and is particu- 
larly abundant near cities. Other artemisias which should be mentioned 
are California mugwort (A. hctcrophylla), gray sage (A. Wrightii) and 
prairie sage (A. gnaphalodcs) which are common throughout much of the 
region, and the dragon sagewort (A. dracunculoides) which occurs spar- 
ingly in the eastern part of the region, and silvery wormwood (A. fili folia) 
which is considered a possible cause of hayfever in the region of Denver. 


The entire Rocky Mountain region has been made the subject of an exhaustive 
study by STIER, HOLLISTER and BONSER (1930) and reported on together with their 
study of Washington and Oregon referred to elsewhere (p. 203). These authors fur- 
nish a list of all the plants of the region known to cause hayfever and those with hay- 
fever possibilities, giving their time of flowering, their life zones or relative elevations 
at which they live, and their abundance in the five different ecological districts into 
which they find the Rocky Mountain region may be divided. 

Roger P. Wodehouse 208 Hayfever Plants 

Foss (1927) reports from Missoula on the hayfever conditions of Montana. He 
finds that the three hayfever periods there are: 1. March and April due to the pollen 
of trees, 2. May and June due to the pollen of grasses, 3. July to frost due to the 
pollen of Russian thistle, sagebrushes and mugworts, and poverty weed, the latter 
period accounting for over 60 per cent of all hayfever in Montana. 

BARRETT (1934) reports a study of the hayfever conditions in and about Salt Lake 
City. He presents a table of all the plants of the region known to cause hayfever or 
with hayfever possibilities, together with their periods of bloom, their abundance, and 
the abundance of their pollen. He also reports the results of counts of atmospheric 
pollen slides exposed at various places in the state throughout the summer. He finds 
that: "From the standpoint of pollen production and plant distribution, the most im- 
portant anemophilous plants of the intermountain states rank as follows : (1) Gramineae 
grasses (2) Chenopodiaceae Russian thistle, saltbushes, summer cypress [Ko- 
chia] (3) Artemisia sages (4) Ambrosiaceae ragweeds". Tree hayfever he finds 
to be caused principally by scrub oak and boxelder ; "Nearly half the shade trees lining 
the streets of Utah towns are boxelders". Grass hayfever he finds to be caused by 
bluegrass, redtop, orchard grass, timothy. The late-summer weed hayfever by Russian 
thistle, the artemisias and ragweeds. The latter, on account of the greater toxicity of 
their pollen, are more important than the number of and the amount of pollen would 
suggest. The author also finds that dandelion is an important cause of hayfever : 
"Four per cent of the hayfever sufferers are sensitive to it. Seven cases have been 
encountered in which it was the sole or major factor". 

ANDERSON (1930), reporting on Utah, gives a classified list of all hayfever plants 
and those with hayfever possibilities, with their times of flowering and relative im- 
portance. He also stresses the observation that dandelion may cause severe hayfever 
with a few individuals. 

TEMPLETON (1924) reports a study of the Sonoran belt of the Intermountain dis- 
trict, the semi-arid non-agricultural part of Utah from 5000 to 7500 feet elevation. The 
principal trees are found to be junipers and poplars, but these flower before any hayfever 
begins so can be of no importance. The principal causes of hayfever are found to be 
the grasses, Russian thistle and other chenopods, and sagebrush. 

MTJLLIN (1922) reporting from Colorado Springs on the hayfever conditions of 
Colorado, furnishes a list of 66 species of plants known to cause or suspected of caus- 
ing hayfever, giving their periods of flowering and characteristic habitats ; and he em- 
phasizes the fact that hayfever in Colorado is very much a local problem. He finds 
the principal causes to be Russian thistle, lambsquarters and burning bush among the 
Chenopodiaceae, and the sageworts (Artemisia} among the Compositae. Ragweed he 
finds to be important only in and about the cities of the eastern slope of the mountains, 
while sagebrush and saltbrushes are the most important on the western slope. Rag- 
weeds, Russian thistle and other introduced weeds drop out at elevations between 6000 
and 7000 feet, but the artemisias ascend to 9000 feet, and sagebrush and timothy even 
higher. Burning bush, while an important weed at Pueblo, he finds does not occur at 
Colorado Springs outside of cultivation. But this was in 1922, cf. SERVICE 1934. 

WOLF (1924) reporting from Pueblo finds that the chenopods and amaranths are 
the most important causes of hayfever, the principal species being Russian thistle, burn- 
ing bush, saltbush, lambsquarters, carelessweed and seablite (Dondia). Sensitization 
to one of these he finds implies sensitization to all. Members of the Artemisia group 
are also found to be important in this region, but neither ragweed nor timothy are 
abundant, and prairie ragweed, though abundant, seems to be unimportant giving re- 
actions with only 5 per cent of the cases tested with its pollen. 

WARING (1925, 1926) in association with MAXY POPE reports a survey of the city 
and county of Denver. The authors furnish a pollen calendar of all the plants known 
or suspected of causing hayfever. They note that the short, tall and western ragweeds 
are common along the roadsides. Poverty weed (Iva axillaris) is common in low dry 
places. The common species of Artemisia are silvery wormwood and prairie sage (A. 
gnaphalodes) . Pasture sage occurs but is not as common here as at lower elevations. 
The commonest weeds on Denver vacant lots they find are Russian thistle, burning 
bush, lambsquarters and prairie ragweed. And the pollen most frequently encountered 

Chapter IV _209 Regional Surveys 

on their slides are of Russian thistle, burning bush, lambsquarters, tall ragweed, prairie 
ragweed and bur ragweed. 

WARING and POPE (1927) report that the " 'cotton', the hair tuft of the seed of the 
cottonwood tree, is a not uncommon cause of hayfever in Denver". It is, however, not 
regarded as the primary cause of cottonwood hayfever, serving rather to prolong the 
hayfever symptoms long after the pollen has ceased to be in the air. 

JOHNSON (1938) reporting his experiences with hayfever in Denver, finds tree 
hayfever, occurring from March to May, to be principally due cottonwoods ; grass hay- 
fever, occurring from May to July, to June grass, orchard grass, timothy, wheatgrass, 
and redtop; weed hayfever, occurring from July to October, to Russian thistle, sages, 
ragweed and pigweed. He finds that the 'cotton' of the cottonwood trees is a factor in 

SERVICE (1934) reports a survey of the region of Pikes Peak, Colorado Springs 
and Manitou. He furnishes a pollen calendar of all hayfever plants and hayfever 
suspects. He reports that the common trees of this district are boxelder, the cotton- 
woods (Popuhts acuminata, P. anguslifolia, P. Sargcntn, P. trcmuloides) , birch, ash 
and juniper all of which are common on city streets or in canyons. There are many 
grasses among which he finds the most important to be redtop, Colorado bluestem 
(Agropyron Smithii), annual bluegrass, June grass, six-weeks grama (Boutcloua 
procumbent] . Among the Amaranth-Chenopod group the commonest were found to 
be western waterhemp, pigweed, lambsquarters, burning bush and Russian thistle. 
The short, tall and western ragweeds were also found to be very common and the 
artemisias, especially Artemisia jrigida, A. ludoviciana and A. tridcntata. 

X. Plains and Prairies (North Dakota, South Dakota, Nebraska, 
Kansas, Minnesota) : 

In this region the same three hayfever seasons may be recognized as in 
the eastern regions, extending through approximately the same periods of 
the year, but a distinguishing characteristic is that here the ragweeds do 
not hold universally the position of dominance that they do in the East. 
This position is disputed with them in parts of the region by Russian thistle, 
the artemisias, western waterhemp and various other western and southern 
species. In fact this is the region of transition between the East and the 
West. DURHAM (1933d) has found that at Pierre, in the central part of 
South Dakota there is about half as much Russian thistle as ragweed pollen 
in the air. Westward of this point Russian thistle gains the ascendency, 
eastward the ragweeds. The same author finds that western Nebraska is 
the center of an ever-widening area in which burning bush, a dominant 
hayfever plant of Colorado, is becoming a serious hayfever menace; at 
North Platte three fourths of all the chenopod-amaranth pollen in the air 
is of this species. In the eastern part of the region, however, these plants 
are unimportant. 


Birches. Of the several species of Betula which occur in this region 
the most important is the paper or canoe birch. It is the common species 
in Minnesota, the Dakotas and northern Nebraska. Yellow birch (B. lutea) 
occurs commonly in Minnesota but scarcely elsewhere in the region. Red 
birch (B. nigra) occurs sparingly in swamps and along the banks of streams 
and ponds in the eastern and southern part of Minnesota. The introduced 
low birch (B. pumlla) also occurs in parts of Minnesota, and the eastern 
gray birch (B. populifolia) is recorded by DUKE (1926) in Kansas City, 

Roger P. Wodehouse 


Hayfever Plants 

(North Dakota, South Dakota, Nebraska, Kansas, Minnesota) 




















Alnus incana (Speckled alder) ... 



Populus* (Poplars, cottonwoods) 


Ulmus* (Elms) 


Acer Negundo (Boxelder) 


Acer* (Maples) 


Salix* (Willows) 


Betula* (Birches) 


Kraxinus* (Ashes) 

Celtis occidentalis (Hackberry) 
Quercus* (Oaks) 



Platanus occidentalis (Sycamore) 
Juglans (Walnut, Butternut) 





Carya (Hickories) 



Plantago lanceolata (English plantain). 

Rumex Acetosella (Sorrel dock) 





Anthoxanth. odorat. (Sw. vernalgrass) . . 
Poa pratensis (June grass) 





Secale cereale (Rye) . 



Brornus* (Brome grasses) 




Lolium perenne (Perennial ryegrass)... 
Koeleria cristata (Western Junegrass) . . 
Poa compressa (Canada bluegrass) 
Dactylis glomerata (Orchard grass) 
Phalaris arundinacea (Reed grass) 
Phlcum pratense (Timothy) 







Agropyron Smithii (West, wheatgrass) 
Agropyron repens (Quack grass) 
Agrostis alba (Redtop) 






Avena fatua (Wild oat) 



Hordeum jubatum (Squirreltail grass). 
Festuca elatior (Meadow fescue) 
Beckmannia Sizigachne (Sloughgrass) . . 
Cynodon Dactylon* (Bermuda grass) 
Chenopodium album* (Lambsquarters) 
Amaranthus retroflexus (Pigweed) .... 
Amaranthus spinosus* (Spiny amaranth) 
Acnida tamarisc.* (West, waterhemp) . . 
Salsola Pestifer* (Russian thistle) 
fCocbia scoparia (Burning bush) 









Artemisia filifolia (Silvery wormwood).. 
Artemisia Absinthium (Absinth sage).. 
Artemisia vulgaris (Wormwood) 
Artemisia Abrotanum (Southernwood). 
Artemisia caudata* (Tall wormwood) 
Artemisia ludoviciana (Prairie sage)... 
Artemisia frigida (Pasture sage) 
Artemisia dracunculoides (Dragon sage) 
Artemisia serrata (Sawleaved mugwort) 
Artemisia biennis (Bienn. wormwood).. 
Artemisia canadensis* (Can. wormwood) 
Artemisia tridentata* (Sagebrush) 
Artemisia annua (Annual sagewort) .... 
Amb. psilostach. (West, ragweed) 
Ambrosia trifida (Tall ragweed) 



















Ambrosia elatior (Short ragweed) 
Ambrosia bidentata* (So. ragweed) 
Iva axillaris (Poverty weed) 
Iva ciliata* (Rough marshelder) 
Cyclachaena xanthifolia* (Burweed) 
Franseria acanthicarpa* (Bur ragweed) 
Xanthium* (Cockleburs) 









Cannabis sativa* (Hemp) 





* Discussed in the accompanying paragraphs. 

Chapter IV 211 Regional Surveys 

and other cultivated forms are found commonly about the towns and cities. 
All flower at about the same time and may occasion a severe type of hay- 
fever. Besides the birches and alders, other members of the birch family 
which commonly occur are the hazels (Corylus americana and C. rostrata) 
flowering in March and April, the ironwood (Ostrya virginiana) and blue- 
beech (Carpinus caroliniana) flowering in April and May. 

Maples. Silver maple {Acer saccharinum) occurs rather commonly 
almost throughout the region, and red maple (A. rubrum) principally in 
the eastern part. 

Poplars. Many species of Populus occur in this region. P. tremu- 
loides, P. grandidentata, P. deltoides and P. balsamifera are reported by 
ELLIS and ROSENDAHL (1933) as the most important in Minnesota, and 
DUKE (1926) reports the necklace poplar (P. virginiana) for Kansas City. 

Willows. ' Many species of Salix occur. S. discolor, S. humilis 
Marsh., S. cordata MuhL, S. amygdaloides Anders., S. fragilis and S. alba 
are reported by ELLIS and ROSENDAHL but are not regarded as important. 

Elms. The principal species of Ulmits are white and slippery elms 
( U. americana and U. fulva) which are widely distributed. The Siberian 
elm (U. piimila) and cork elm (U. racemosa Thomas) are less common, 
the latter confined in this region principally to Minnesota and northern 

Ashes. White ash (Fraxinus americana), green ash (F. lanceolata) 
and black ash (F. nigra Marsh.) occur commonly in Minnesota and to a 
lesser extent in the Dakotas and Nebraska. 

Oaks. Six species of oak (Quercus inacrocarpa Michx., Q. velutina, 
Q. ellipsoidalis E. J. Hill, Q. bor calls, Q. coccinca and Q. alba) are recorded 
by ELLIS and ROSENDAHL as common and likely to cause hayfever in Min- 
nesota. The same species, however, also occur to a certain extent elsewhere 
in the region. 


This is primarily a region of grasses. In them lie the great inherent 
riches of the plains and prairies, yet the grasses are no more important as 
causes of hayfever here than elsewhere for the native species are nearly 
harmless. It is the introduced weeds and agricultural grasses that have to 
be reckoned with. GATES (1937) in his delightful little book on the grasses 
of Kansas states : "The pollen of certain grasses causes hayfever in human 
beings. Chief among these grasses in Kansas are orchard grass (Dactylis 
glomerata), bluegrass (Poa pratensis), meadow fescue (Fcstuca clatior), 
rye or ray grass (Lolium perenne), western wheat grass (Agropyron 
Smithii), rye (Secale cerealc), tall oatgrass (Arrhenatherum elatius), 
timothy (Phleum pratcnse), redtop (Agrostis alba), Bermuda grass 
(Cynodon Dactylon), sweet vernalgrass (Anthoxanthum odoratum), John- 
son grass (Sorghum halepense), and corn (Zca Mays)". It is interesting 
to note that of all these only western wheatgrass is native to the state, and 
it is among the least important of the list. 

Brome Grasses. Bromus inermis, B. secalinus, B. ciliatns L. and 

Roger P. Wodehouse 212 Hayfever Plants 

B. horde aceus are common throughout much of the region but are of little 
or no importance. 

Fescue Grasses. Besides meadow fescue are found about ten other 
species. Of these six-weeks fescue (Festuca octoflora) and sheep fescue 
(F. ovind) are widely distributed and regarded by ELLIS and ROSENDAHL 
as having hayfever possibilities. 

Bermuda Grasses. Cynodon Dactylon occurs only in Kansas, and in 
parts of the state appears to be a factor to be reckoned with. Johnson grass 
occurs in fields and waste places in Kansas and is even sometimes culti- 
vated in the southern part, but it does not appear to be an important factor 
in hayfever. 


Russian Thistle. Salsola Pestifer is an important cause of hayfever 
throughout all this region except the northern and eastern parts of Minne- 
sota, and accounts for possibly 20 per cent of the hayfever. Its prevalence is 
largely due to excessive grazing and other mismanagement of the soil. 
Since its introduction it has come to possess a large part of the land which 
was formerly occupied by native prairie grasses. 

Spiny Amaranth. Amaranthus spinosus occurs throughout the region 
but only in the southern part is it abundant enough to be a factor of impor- 
tance; it is recorded by DUKE and DURHAM (1924) as a possible cause of 
hayfever in Kansas. 

Waterhemp. Two species of Acnida occur in this region. By far the 
most important is the western waterhemp (A. tamariscina) . It is extremely 
abundant in Kansas but does not extend in effective quantities northward. 
Instead it is replaced by its less important relative A. tuberculata, rough- 
fruited waterhemp. 

Docks. Besides the sorrel docks several other species of Rumex 
occur. ELLIS and ROSENDAHL (1933) record curly dock, peach leaved 
dock (R. altissimus Wood), golden dock (R. persicarioides L.), pale dock 
(R. mexicanus L.), bitter dock (R. obtusifolius) and the great water dock 
(R. britannica L.). 

Mugworts and Wormwoods. Artemisias are among the most impor- 
tant causes of hayfever in the region. RYDBERG (1932) describes 30 species 
occurring. Those listed in the flowering calendar, except the first and last, 
are regarded by ELLIS and ROSENDAHL (1932) as important; common 
sagebrush occurs only in the extreme western part of the Dakotas and 
Nebraska and the sand sagebrush in the western part of Kansas, where they 
may be of some local importance. Artemisia canadensis is a northern species 
only entering the region along the Canadian border, but it is believed to 
be of local importance in northern Minnesota. A. caudata and A. dracuncu- 
loides are the commonest species, growing in sandy soil, especially on dry 
slopes and sandy outwash plains, and in vacant lots and waste places within 
the cities. ELLIS and ROSENDAHL (1932) state that the three introduced 
species A. Abrotanum, A. vulgaris and A. Absinthium have become natu- 
ralized to some extent in Minnesota and the eastern part of the Dakotas. 
They are also frequently grown as ornamentals, the first used as a hedge 

Chapter IV 213 Regional Surveys 

plant on account of its robust character, and for this reason hayfever patients 
are liable to come in very close contact with them. 

Ragweeds and False Ragweeds. The tall, short and western ragweeds 
are extremely abundant throughout the entire region and generally speaking 
their pollen constitutes the worst cause of hayfever. The southern or lance- 
leaved ragweed is a plant of the southern prairies, abundant in Kansas 
and occurring as far north as southern Minnesota, but not recorded for 
the Dakotas. RYDBERG (1932) records four species of Franseria for this 
region. Of these F. acanthicarpa is widespread in the Dakotas but occur- 
ring only sporadically elsewhere. F. tenuijolia, F. discolor and F. tomentosa 
also occur in parts of the region but appear to be unimportant. Prairie 
ragweed (Cyclachaena xanthijolia) is most important in the Dakotas and 
Nebraska but occurs more or less abundantly throughout. Rough marsh- 
elder (Iva ciliata) is a southern species and occurs in this region only in 
Kansas and southern Nebraska. 

Cockleburs. Three species of Xanthium are widespread, frequenting 
low moist places, sandy shores and alluvial bottom lands, fields and waste- 
places. One of the commonest is the great clotbur (X. speciosum) which is 
a particularly heavy pollen shedder. Beach clotbur (X. echinatum Murr.) 
and common cocklebur (X. pennsylvanicum) are also common. 

Hemp. Cannabis sativa is abundant throughout, and is stated by 
DURHAM (1933d) to outrank ragweed in some areas along the Mississippi 
and Missouri Rivers, but Omaha is the only place investigated where it 
assumes allergic importance. The reason for its abundance in some parts 
of Nebraska, as pointed out by MAcQuiDDY (DURHAM 1935&), is that in 
about the year 1889 hemp was introduced into this region for making rope. 
It was first cultivated at Fremont, Nebraska, later at Omaha, Lincoln and 
Columbus. Though it is no longer cultivated, it has escaped and now 
ranges widely from these places. 


The first study of the hayfever conditions of any part of this region appears to be 
that of DUKE and DURHAM (1924), "A Botanic Survey of Kansas City and Vicinity". 
They find that the most important trees are boxelder, sycamore, cottonwood, ash, 
hazel, black walnut, hickory and oak, their flowering periods extending from March to 
June but occurring mostly in April and May. The most important grasses they find 
to be rye, June grass, timothy, slough grass and orchard grass, flowering from the 
middle of May to the middle of July. Sudan grass and Johnson grass, while they 
occur, are found to be unimportant. Among the weeds, flowering mostly from mid 
August to frost, they found the most important to be the short and tall ragweeds, 
ranking far ahead of all others, and of lesser importance, southern ragweed, Russian 
thistle, burning bush and wormwoods. 

DUKE (1926) furnishes a pollen calendar for Kansas City accompanied by descrip- 
tions and photographic illustrations of all the most important hayfever plants. 

A series of exhaustive researches into the pollen situation in Minnesota and the 
Dakotas has been conducted by ELLIS and ROSENDAHL (1932, 1933, 1934). In the first 
of these studies, which deals only with late-summer hayfever, the authors furnish a list, 
with their times of flowering, of all species comprising the ragweed and wormwood 
groups and giving the importance and distribution of each within the three states. They 
find that all of the many species of Artemisia are important, and that reactions of hay- 
fever sufferers to their pollen are more severe than to that of ragweed, and, with many 

Roger P. Wodehouse 214 Hayfever Plants 

cases, allergenically distinct. The most important ragweeds they find are the tall and 
short. The western ragweed is found scattered throughout the area on sandy soils in 
fields, pastures and open situations, and occasionally in openings in the northern conifer- 
ous forest, enjoying the widest distribution of all the ragweeds in the region. It is 
liable to be a source of trouble to patients who seek the north woods for relief. Next 
in importance to the ragweeds is found to be prairie ragweed. In the second paper which 
deals with the hayfever situation in Minnesota during all seasons, the authors furnish 
a list of all plants with hayfever possibilities, their dates of flowering and relative 
abundance. The species are assembled according to their biological relationships into 
24 groups which may be used in combination for diagnosis and treatment instead of the 
individual species. It is found that the ragweed group, containing the ragweeds, bur 
ragweed, prairie ragweed and cockleburs, is the most important; the sage-wormwood 
group, containing all the artemisias, is next in importance; then follow the groups of 
grasses and of pigweeds. The oak, elm and ash groups are found to be the most impor- 
tant among the trees, but all much less so than the groups just mentioned. The third 
paper of these authors deals with the diagnosis and treatment of hayfever with special 
reference to Minnesota. They furnish 60 maps showing the distributional abundance 
within the state of 60 species of hayfever plants. They find that the importance of 
the dock group, including various species of Rutncx, Polygonwn and Rheum, is prob- 
ably greater than has generally been recognized. Approximately 20 per cent of the 
hayfever cases studied were found to be sensitive to pollen of this group. But the most 
important group is that of the ragweeds, and the authors find that several members 
of this group are extending their range and are becoming established in localities where 
they were formerly unknown. 

ROSENDAHL, ELLIS and DAHL (1940) continuing this work, report a four-year 
study of "Air borne Pollen in the Twin Cities Area with Reference to Hayfever". They 
list all the important groups of hayfever plants and furnish graphs showing their pollen 
concentration throughout the season. 

STOSSER ( 1942) reports from Minneapolis a study of hayfever in 413 children. Of 
these 306 were found to be sensitive to ragweed, 209 to the sage-mugwort group, 146 
to Russian thistle, 72 to grasses, and fewer to the trees, plantain and other weeds. 

VAUGHAN (1931) furnishes a pollen calendar of the hayfever plants of Kansas 
City compiled by DUKE (1926), and of the Prairies and Plains compiled by BALYEAT 
(1930). HANSEL (1936) presents a brief but comprehensive summary of the published 
reports dealing with the hayfever conditions in the Plains and Prairies. 

WALTON (1939, 1940) and WALTON and DUDLEY (1940) have recently reported 
the results of their studies in Manitoba and western Canada. They find that the early 
hayfever season begins about April 20, and is due to the poplars, hazels, willows, 
birches, boxelder, elm, ash and scrub oak. Summer hayfever begins in June, and is 
due to the grasses and plantain. The ragweed pollen counts they find to be low but the 
sages and Russian thistle are important in the fall. 


Allergen. A substance which produces an allergic manifestation in an allergically 
sensitized human being. 

Allergy. A specific hypersensitiveness among human beings regardless of its 
cause or origin. Such maladies as hayfever, asthma, urticaria, angioneurotic oedema, 
some forms of eczema and migraine are among the commonest manifestations. Derma- 
titis from poison ivy, primrose and other plants is included by some allergists, as indeed, 
is indicated by the above definition, though such is excluded by other allergists. 

Amphiphilous. Pollinated by the agencies of both insects and wind, as with 
willows and some maples. 

Anemophilous. Pollinated by the agency of wind, as in pine and ragweed. 

Annual. Flowering and fruiting in the first year or season and then dying, as in 
short ragweed and Russian thistle. 

Anther. The sac or sacs containing the pollen, the essential part of the stamen. 

Aperture (pollen). See Germinal aperture. 

Appressed. Adpressed, lying close and flat. 

Arachnoid. Cobwebby, of slender entangled hairs. 

Aspidate (pollen). With pores surrounded by shield-shaped thickenings. 

Awn. A slender bristle at the end of an organ, in the grasses a continuation of 
the midnerve of a glume or lemma. 

Axil. The upper angle formed by a leaf or branch with the stem. 

Axillary. Borne at or pertaining to an axil. 

Bipinnatifid. Twice pinnatifid. 

Biennial. Lasting two years, flowering and fruiting in the second, as in carrot. 

Canescent. Grayish white or hairy, the surface covered with fine white hairs 

Calyx. The outer perianth of a flower. 

Carpel. A simple pistil or one member of a compound pistil. 

Catkin. Ament. A scaly deciduous spike of flowers. 

Cespitose. Growing in tufts. 

Connective. The filament or tissue connecting the cells of an anther, particularly 
when the cells stand apart from each other. 

Corolla. The inner perianth of a flower. 

Corymb. A flat-topped or convex open flower cluster, with pedicels of unequal 
length, progressing in its flowering from the margin inward. 

Cotyledon. Seed leaf. 

Culm. The jointed stem of a grass, which is usually hollow except at the nodes. 

Cyme. A flattish flower cluster in which the terminal or central flowers bloom 

Deciduous. Falling away at the close of the growing period. 

Decumbent. Reclining, but with the summit ascending. 

Dentate. Toothed with the teeth standing directly outward. 

Digitate. Parted or divided like the fingers of the hand, applied usually to the 
palmate division or lobing of leaves. 

Dioecious. Having only distinct staminate and pistillate flowers, and these borne 
on separate plants, as in poplars and willows. 

Disk. In Compositac the tubular flowers collectively, as distinct from the ray 

Entire. Margin not toothed or indented in any way. 

Entomophilous. Pollinated primarily by the agency of insects, as in orchids, 
sweet peas and goldenrods. 

Exine. The outer wall of a pollen grain. 

Fascicle. A close bundle or cluster. 

Filament. The part of a stamen which supports the anther. 

Floret. A small flower, one of a cluster, as the individual flowers of the heads 
of Compositoe; the lemma and palea with included stamens and pistil among the 

Roger P. Wodehouse 216 Hayfever Plants 

Furrow (pollen) . See Germinal furrow. 

Germinal aperture. A hole in the furrow membrane or exine through which a 
pollen tube may emerge. 

Germinal furrow. A groove or elongate opening in the exine of a pollen grain, 
either enclosing a germ pore or serving directly as the place of emission of the pollen 

Germinal papilla. A dome-shaped protrusion through a germinal aperture of a 
pollen grain; the pollen tube "Anlage". 

Germ pore. See Germinal aperture. 

Glomerule. A compact or condensed head-like cyme. 

Glumes. The pair of bracts at the base of a spikelet among the grasses. 

Halophyte. A plant growing in salty or alkaline soils, as pickleweed, greasewood. 

Herb. A plant with no persistent woody stem above ground. 

Herbaceous. Having the characters of an herb; leaf like in color and texture. 

Hyaline. Transparent or translucent. 

Intine. The inner wall of a pollen grain. 

Involucre. A circle of bracts subtending a flower cluster. 

Laciniate. Cut or shredded into narrow divisions. 

Lemma. The bract of a spikelet above the pair of glumes among the grasses. 

Lenticels. Small areas in the bark where the cork cells are somewhat loose and 
spongy allowing a small amount of gas interchange between the tissues below and the 
air outside. 

Lodicule. Among the grasses, minute hyaline scale-like organs at the base of the 
stamens whose function is the opening of the floral envelope at anthesis. 

Monoecious. Having only distinct staminate and pistillate flowers, and these on 
the same plant, as in walnuts, pines and ragweeds. 

Mucronate. Tipped with a short soft spine. 

Node. The place upon the stem which normally bears a leaf or leaves; among 
the grasses, a joint of the culm. 

Operculum. A thickening of measurable bulk and clearly defined of the pore 
membrane of a pollen grain, as in that of grass. 

Ovary. The part of the pistil that contains the ovules. 

Palet, Palea. The upper bract which, with the lemma, incloses the flower among 
the grasses. 

Palmate. Radiately lobed or divided, as of a leaf. 

Panicle. A loose irregularly compound inflorescence with pedicillate flowers. 

Papilionaceous (corolla). Butterfly shaped, having a standard, wings and keel, 
as in sweet pea and locust. 

Pedicel. Stem of a flower in a flower cluster. 

Peduncle. Stalk or stem of a flower or flower cluster. 

Peltate. Shield shaped, and attached to its stalk inside its margin. 

Perennial. Lasting year after year, as in western ragweed, Bermuda grass and 

Perfect (flower). Having both pistil and stamens, as in rose or privet. 

Perianth. The floral envelope, consisting of the calyx and corolla or calyx alone. 

Petiole. Stalk of a leaf. 

Pinnate (leaf). Compound, with the leaflets arranged on each side of a com- 
mon petiole. 

Pinnatifid. Cleft in a pinnate manner. 

Pistil. A seed-bearing organ. 

Pore. Sec Germinal aperture. 

Pubescent. Clothed with soft downy hairs. 

Raceme. A simple inflorescence of pedicellate flowers upon a common more or 
less elongate axis. 

Rachilla. A small rachis. Among the grasses applied especially to the axis of a 

Rachis. The axis of a spike or raceme, the prolongation of the peduncle through 
the flower cluster; the axis or midrib of a compound leaf; among the grasses the main 
axis and branches of an inflorescence on which the spikelets are borne. 

Hayfever Plants 217 Glossary 

Ray. In the Compositae, the ligulate corolla of a marginal flower. 

Receptacle. The more or less expanded or produced portion of an axis which 
bears the organs of a flower or (in the Compositae) the collected flowers of a head. 

Rhizome. Underground stem; rootstock. 

Rootstock. Rhizome. 

Scaphoid. Boat shaped. 

Sessile. Without a stalk. 

Spike. An unbranched inflorescence in which the units are more or less sessile 
along a central axis. Ordinarily the units are individual flowers as in plantain, but 
among the grasses they are spikelets as in timothy, and among the Compositae they are 
flower heads as in ragweed. 

Spikelet. A secondary spike; among the grasses the unit of inflorescence, con- 
sisting of two glumes and one or more florets. 

Stamen. A pollen bearing organ. 

Stigma. The part of the pistil receptive to pollen grains and on which they ger- 
minate, usually the apex of the style. 

Stipules. Small supplementary organs or appendages of a leaf, borne in pairs 
at the base of the petiole. 

Strobile. Cone. 

Style. The portion of a pistil between the ovary and stigma, generally contracted 
and often slender. 

Tomentose. Densely pubescent with matted wool. 

Tricolpate (pollen grains). Possessing three meridionally arranged germinal 

Trischistoclasic. The system in which the furrows of pollen grains of the higher 
dicotyledons tend to form, characterized by triconvergent angles. 

Whorl. An arrangement of leaves or other organs in a circle round the stem. 


ABRAMS, L. R. 1923: An Illustrated Flora of the Pacific States, Vol. 1, 557 pp., 1299 
figs. (Stanford University Press). 

1932: The hayfever plants of the western states, Pt. 1 (Bull. Southern Pa- 
cific General Hospital, 1: 162-165, fig. 1-3). 

ALBERT, H. & V. DEBELL 1927: Hayfever in Nevada (Calif, and Western Med. 27: 

American Joint Committee on Horticultural Nomenclature 1924: Standardized Plant 
Names (Salem, Mass.). 

ANDERSON, J. M. 1930: Hayfever plants of Utah (Calif, and West. Med. 33(4) : 

WODEHOUSE & E. B. LAMBERT 1941 : Techniques for appraising air-borne popu- 
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ratus in Aerobiology, National Research Council (Phytopathology 31(2): 201- 

Anonymous 1918: Ragweed (Ambrosia arteniisiifolia) (Dominion (Canada) Dcpt. 
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1942: Hayfever in Latin America (Bol. Of. San. Pan. 21(3): 290-294). 

1943: Another ragweed survey (N. V. State J. Med. 43(13) : 1232). 

AQUARONE, PAUL & L. N. GAY 1931 : A survey of the pollen flora in Baltimore 
during 1929 (/. Allergy 2(5) : 336-345, 7 figs.). 

ASCIIER, M. S. 1941: Psyllium seed sensitivity (/. Allergy 12: 607). 

BABB, M. F. 1939: Orach its culture and use as a greens crop in the Great Plains 
region (U. S. Dcpt. Agric. Circ. 526, 22 pp., 4 figs., 4 tabs.). 

BAILEY, L. H. 1914: The Standard Cyclopedia of Horticulture, 6 vols. (New York, 
Macmillan Co.). 

1924: Manual of Cultivated Plants, 851 pp., 14 figs. (New York, Mac- 
millan Co.). 

1933: The Cultivated Conifers of North America, 403 pp., 48 pis., 114 figs. 

BALL, C. R. 1900: The genus Salix in Iowa (Prof. Iowa Acad. Sci. 7: 135-144). 

1924: Shrubby willows of Indiana. Shrubs of Indiana by CIIAS. C. DEAM 

(Pub. 44 Dept. Conservation, State of Indiana). 

BALYEAT, R. M. 1930: Allergic diseases, their diagnosis and treatment (Philadel- 
phia, F. A. Davis). 

& H. J. RINKEL 1932: Distribution and importance of the paper mulberry 

as a cause of hayfever and asthma in the United States (/. Allergy 3(1) : 7-15, 
6 figs.). 

& T. R. STEMEN 1927 : Hayfever and asthma. Distributon and impor- 
tance of the acnidas as a cause of hayfever and asthma in the United States (Amer. 
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BARRETT, CHAS. E. 1934 : Studies in hayfever. Clinical observations including a bo- 
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BENTHAM, GEORGE 1873: Notes on the classification, history and geographical distri- 
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1930: Tree pollens (Virginia Med. Monthly 57: 170). 

BESSEY, C. E. 1915 : The phylogenctic taxonomy of the flowering plants (Ann. Mo. 
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BIEDERMAN, J. B. 1937: Sensitivity to flowers (Laryngoscope 47(11) : 825-828). 

BLACK, J. H. 1929 : Cedar hayfever (/. Allergy 1 : 71-73) . 

& O. C. DURHAM 1930: Elm pollen as a complicating factor in hayfever 

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Hayfever Plants 219 Bibliography 

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Roger P. Wodehouse 220 Hayfever Plants 

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19336 : The ragweed situation in the southern states (New Orleans Med. & 

Surg. J. 85: 492). 

1933*:: Fall hayfever pollens of Canada (Can. M. A. J. 28: 604). 

1933d: Complicating factors encountered in ragweed hayfever (/. Amer. 

Med. Assn. 100: 1848-1850). 
I933e: The ragweed season of 1932 in the United States, Canada and 

Mexico (J. Allergy 4: 105-113, fig. 1-5, tab. 1). 

1935a: Six fall seasons in Indiana (J. Indiana Med. Assn. 28: 183-184). 

19356: The pollen content of the air of North America (/. Allergy 6: 

1935<r: Pollen studies in selected areas (7. Amer. Med. Assn. 104(17): 

1936: Your Hayfever (New York, The Bobbs Merrill Co.). 

Hay fever Plants 221 Bibliography 

1937: Evaluation of the ragweed resort areas of North America (/. Al- 
lergy 8(2): 175-180). 

1941: Atmospheric allergens in Alaska (/. Allergy 12: 307). 

1943: Kochia scoparia as a factor in inhalant allergy (/. Allergy 14(2) : 


DUTTON, L. O. 1938: Beet pollen and beet seed dust causing hayfever and asthma 
(/. Allergy 9: 607). 

EFRON, B. G. 1942-1943 : Tests with insect allergens (Internal. Correspondence Club 
of Allergy 6: 20). 

ELLIS, R. V. & C. O. ROSENDAHL 1932: Fall hayfever in the upper Mississippi Val- 
ley with special reference to Minnesota and the Dakotas (Journ. Lancet 52: 

& 1933 : A survey of the causes of hayfever for the state of Min- 
nesota (Minn. Med. 16: 379-389). 

& 1934: The diagnosis and treatment of hayfever with special 

reference to Minnesota (Minn. Med. 17: 378-383). 

EMERSON, A. J. & C. M. WEED 1918 : Our American trees and how to know them 

ERDTMAN, G. 1935: Investigations of honey pollen (Svensk Bot. Tidskr. 29(1): 

1937: Pollen grains recovered from the atmosphere over the Atlantic 

(Meddel. Goteborgs Bot. Tr'ddg. 12: 185-196). 

1943: Pollen Analysis, 239 pp. (Waltham Mass., Chron. Bot. Co.) 

FASSETT, N. C., L. McGARY & L. F. BATES 1938: Hayfever plants of the Middle 
West (Madison, Wis., John S. Swift Co.). 

FEINBERG, S. M. 1929: Progress in hayfever (/. Lab. 6- Clin. Med. 14(8) : 726-746). 

1932: Hayfever in the North Central States. Its causes and treatment 

(III. Med. J. 61:429-433). 

1934: Allergy in General Practice (Philadelphia, Lea and Febiger). 

& T. B. BERNSTEIN 1940: Asthma and hayfever. Contributions during 

1939 (Annual review) (/. Allergy 11(3) : 281). 

& O. C. DURHAM 1933 : Hayfever in Chicago and suburbs. Clinical, field 

and air observations (///. Med. J. 63 : 464) . 

& M. J. STEINBERG 1933: Studies on pollen potency (/. Allergy 5: 19). 

FERNALD, M. L. & LUDLOW GRISCOM 1935 : Three days botanizing in southern Vir- 
ginia. Ambrosia artemisiaefolia and its variations in temperate North America 
(Rhodora 37: 167-189). 

FIGLEY, K. D. 1926: Hayfever, its diagnosis and treatment (Ohio State M. J. 22: 

FIRBAS, F. 1937: Der Pollenanalytische Nachweis des Getreidebaus (Zeit. {. Bot. 
31: 447-478, figs. 1-4). 

FLINT, C. L. 1895: Grasses and Forage Plants. Ed. 2 (Boston). 

FOERSTE, A. F. 1882: Notes on Ambrosia trifida (Bot. Gas. 7: 40-41). 

FOSKETT, H. H. 1929: Some observations on hayfever in the Willamette Valley 
(The Med. Sentinel 37: 565). 

Foss, A. R. 1927: Hayfever in Montana (Minnesota Med. 10: 587). 

Fox, E. C. 1941 : Mesquite wood dermatitis (Arch. Derm. & Syphil. 44: 1098). 

FREEMAN, J. 1927 : Treatment of hayfever (Lancet 1 : 940-941). 

FRENCH, S. W. 1930 : Pollens which cause hayfever in south central Texas (/. Al- 
lergy 1:286-291 fig. 1-4). 

FREUD, E. M. 1935: Hayfever in the Capitol district (N. Y. Med. Rec. 141: 357- 

GARRETT, A. O. 1917: Spring Flora of the Wasatch region, 144 pp. (Lancaster, Pa.). 

GATES, F. C. 1937: Grasses in Kansas (Rept. Kans. Board Agric. 55, No. 220-A). 

1940: Flora of Kansas (Topeka, Kans.). 

1941: Weeds in Kansas (Rept. Kans. Board Agric. 60, No. 243). 

GAY, L. N., H. CURTIS & T. NORRIS 1941 : A pollen survey of the islands of Ber- 
muda (Bull Johns Hopkins Hosp. 68: 179). 

GEDDES, W. N. 1875 : Some great ragweeds (Ambrosia trifida L.) (Bot. Gaz. \ : 

GEORGE, E. J. 1936: Growth and survival of deciduous trees in Shelter-belt Experi- 
ments at Mandan, North Dakota, 1915-1934 (17. S. Dept. Agric. Technical Bull. 
496: 1-48). 

Roger P. Wodehouse 222 Hayfever Plants 

GLEASON, H. A. 1922: Vernonia (North American Flora 33(1) : 53-94). 
1923a: Evolution and geographical distribution of the genus Vernonia in 

North America (Amer. J. Bot. 10: 187-202). 

19236: The Bolivian species of Vernonia (Amer. J. Bot. 10: 297-309). 

GOLDSTEIN, M. B. 1931 : Dermatitis venenata due to Chrysanthemum leaves (/. 

Amer. Med. Assn. 96: 1680-1681). 

GRAY, ASA 1895 : Field, Forest and Garden Botany. Revised by L. H. BAILEY. 
1908: New Manual of Botany. Ed. 7, revised by B. L, ROBINSON and 

M. L. FERNALD, 926 pp., 1036 figs. (New York). 
GRECO, J. B., A. OLIVEIRA LENIA & A. TUPINAMBA 1942: The pollen content of the 

air in Belo Horizonte, Brazil (/. Allergy 13(4) : 411-413). 
GREENHOUSE, C. A. & MARION SULZBERGER 1933 : The common weed tansy (Tanace- 

tum vulgare) as a cause of eczematous dermatitis (/. Allergy 4: 523-526). 
GRIFFITHS, DAVID 1912: The grama grasses (Contrib. U. S. Nat. Herbarium 14(3), 

GROH, H. & W. H. MINSHALL 1940 : Ragweed situation in eastern Canada in relation 

to hayfever (Can. M. A. J. 43: 258). 
GUTMANN, M. J. 1941 : The first report on hayfever in Palestine (/. Allergy 12(2) : 


HALL, H. M. 1917: The relation of farm weeds to hayfever (Monthly Bull. (Sacra- 
mento, Calif.) 6(2) : 44-47, fig. 8-9). 

1918: Walnut pollen as a cause of hayfever (Science 68(221) : 516-517). 

1922: Hayfever plants of California (U. S. Pub. Health Repts. 37(14) : 

1928: The genus Haplopappus, a phylogenetic study in the Compositae 

(Carnegie Inst. Pub. 399: 1-391). 
& F. E. CLEMENTS 1923: The phylogenetic method in taxonomy; the 

North American species of Artemisia, Chrysothamnus and Atriplex (Washington). 
HANSEL, F. K. 1936: Allergy of the nose and paranasal sinuses (St. Louis, C. V. 

HARA, H. J. 1939: Hayfever among Japanese, III. Studies of atmospheric pollen 

in Tokyo and Kobe (Arch. Otolaryngol. 30: 525). 
HAWES, R. C., W. S. SMALL & HYMAN MILLER 1942 : An apparatus for determining 

the pollen content of the air and notes on pollen survey methods (J. Allergy 13(5) : 


HEINBERG, C. J. 1930: Spiny amaranth (/. Fla. M. A. 17: 221). 
HENRY, J. P. & A. L. HERRING 1930: A botanical survey of Memphis, Tenn. and 

surrounding territory (/. Allergy 1: 163-169). 
HITCHCOCK, A. S. 1920 : The genera of the grasses of the United States with special 

reference to the economic species (U. S. Dept. Agric. Bull. 772, 307 pp., illus- 
1925 : Methods of Descriptive Systematic Botany (New York, John Wiley 

& Sons). 
1935: Manual of the grasses of the United States (U. S. Dept. Agric. 

Misc. Pub. No. 200, 1040 pp., 1696 figs.). 
1936: Manual of the grasses of the West Indies (U. S. Dept. Agric. 

Misc. Pub. 243, 439 pp., 374 figs.). 
& p. c. STANDLEY 1916: Flora of the District of Columbia and vicinity 

(Contrib. U. S. Nat. Herb. Vol. 21). 

HOCH, J. H. & J. J. WARING 1933: Hayfever plants of Charleston, S. C. and vi- 
cinity (/. S. C. Med. Assn. 29: 69-71). 
HODGSON, H. 1935: Report of botanical survey of Bermuda (N. Y. State J. Med. 

35: 27). 
HOUGH, R. B. 1907 : Handbook of the Trees of the Northern States and Canada East 

of the Rocky Mountains (Lowville, N. Y.). 

HOWELL, THOMAS 1903: A flora of northwest America (Portland, Oregon). 
HUBER, HARRY L. 1926: Hayfever in the Chicago territory (///. M. J. 49: 133-138). 
& GEO. F. HARSH 1932: A summer dermatitis caused by a common weed 

(Cyclachaena xanthifolia) (J. Allergy 3: 578-582). 
HULSEY, S. 1933: Pollen counts in Fort Worth, Texas, for the years 1929-1931 

(Tex. State J. Med. 28: 779-789). 
HURWITZ, S. H. 1930: Hayfever, a sketch of its early history (/. Allergy 1: 245). 

Hayfever Plants 223 Bibliography 

JAMIESON, C. A. 1939: A method of distinguishing between pollens of Melilotus 
species, Trijolium hybridum and T. repens (Bee World, September 1939). 

JAMIESON, H. C. 1937: Hayfever in Alberta (Can. M. A. J. 36: 595). 

JEPSON, W. L. 1909: Trees of California (San Francisco). 

1910: The Silva of California (Berkeley, Calif.). 

1925: Manual of the Flowering Plants of California (Berkeley. Calif.). 

JOHNSON, R. P. 1938: The specific treatment of hayfever and pollen asthma in Den- 
ver (Rocky Mt. M. J. 35: 305). 

JONES, K. L. 1936: Studies on Ambrosia (Amer. Midland Nat. 17: 673-700). 

KAHN, I. S. 1924: The botany of southwest Texas with reference to hayfever and 
asthma (/. Amer. Mcd. Assn. 82: 871). 

1926: The asthma problem as it affects the South (So. M. J. 19: 183-186). 

& E. M. GROTHAUS 1930: Tree pollen hayfever and asthma in the South 

(So. Med. J. 23(7) : 662-665). 

& 1931 : Hayfever and asthma due to red cedar and to mountain 

cedar (So. Mcd. J. 24(8) : 729-730). 

KEARNEY, T. H., L. J. BRIGGS, JR., J. W. MCLEAN & R. L. PIEMEISEL 1914 : Indi- 
cator significance of vegetation in Tooele Valley, Utah (/. Agric. Res. 1: 365-417). 

& R. H. PEEBLES 1942 : Flowering plants and ferns of Arizona ( V. S. Dept. 

Agric. Misc. Pub. 423, 1069 pp.). 

KELLY, J. W. 1928 : Methods of collecting and preserving pollen for use in the 
treatment of hayfever (U. S. Dept. Agric., Bur. Plant Industry, Circ. 46: 1-9, 
figs. 1-7). 

KEY, S. N. 1918: The etiology of winter hayfever in Texas (Tex. State J. Med. 
13: 308-309, 2 figs.). 

KOESSLER, K. K. & O. C. DURHAM 1926: A system for an intensive pollen survey 
with a report of the results in Chicago (/. Amer. Med. Assn. 86: 1204). 

LACKEY, J. B. & A. M. GOLTMAN 1934: Botanical aspects of the hayfever situation 
in the Memphis area (/. Tenn. Acad. Set. 9(2) : 133-148). 

LAMSON, R. W. 1931 : Evidence of biological relationships among species of Che- 
nopodiales (Proc. Soc. Ex p. Biol. & Med. 28: 502-504). 

& ALVA WATRY 1933a: The importance of the Chcnopodiaccae in pollin- 

osus; with special reference to Winslow and Holbrook, Ariz. (/. Allergy 4(4) : 
255-283, fig. 1-27, tab. I, II). 

& 1933fr: Anemophilous plants of Seligman, Arizona (J. Allergy 

4(3) : 207-219, fig. 1-4). 

& 1934: Survey of a botanic oasis in the desert of northern Ari- 
zona (/. Allergy 5(4) : 389-405). 

, H. McMiCHAEL & M. STICKLER 1944: Potential pollinosis in a desert and 

coastal city ; a comparative botanic survey of Barstow and Santa Ana, California 
(/. Allergy 15: 21-60). 

LANGLEY, W. D. 1937: Sensitivity to Piqucria pollen with case report (/. Allergy 
9(1) : 60, 61). 

LARUSH, FLORENCE 1934 : The pollen content of the air in Toronto, Canada, 1932 
(/. Allergy 5: 306-317, 3 figs., 10 tabs.). 

LEE, A. B. 1921: The microtomist's vade-mecum (Blakiston, Philadelphia). 

LEWIS, I. M. 1915: The trees of Texas (Bull. No. 22, Univ. Tex.}. 

LINDAU, WALTER & L. N. GAY 1942: Allergy in Germany (A review of "Allergic, 
ein Lehrbuch in Vorlesungen" by K. H. BAAGOE, W. BERGER et al., 1940) (/. Al- 
lergy 13: 494). 

LUDI, WERNER & VOLKMAR VARESCHI 1936: Die Verbreitung, das Bliihen und der 
Pollenniederschlag der Heufieberpflanzen im Hochtale von Davos (Bericht iiber 
das Geobotanische Forschungsinstitut Rubel in Zurich fur das Jahr 1935, Zurich, 

McMiNN, H. E. & EVELYN GRAHAM 1937: Another plant causing hayfever in Cali- 
fornia, Coprosma Baueri Endl., Mirror plant. 

MACQUIDDY, E. L. 1935: Air studies at higher altitudes (/. Allergy 6(2) : 123-127). 

MALLEN, M. S. 1940: Pollens in the atmosphere of Mexico City (Prensa Med. Mex. 
9: 166). 

& p. LYOMRET 1940: Allergic flora of the Valley of Mexico (Prensa Med. 

Mex. 9: 163). 

Roger P. Wodehouse 224 Hayfever Plants 

MALONEY, E. S. & M. H. BROADKEY 1940: Hemp pollen sensitivity in Omaha (Neb. 

State M. /. 25: 190). 

METZGER, F. C. 1932: Hayfever in Florida (/. Fla. M. A. 19: 18). 
1939: The climatic treatment of hayfever and asthma (/. Amer. Med. 

Assn. 112: 29-32). 
MILLSPAUGH, C. F. & E. E. SHERFF 1922: Xanthium (The North American Flora 

33(1) : 37-44, New York). 
MORENO, G. Ruiz & A. E. BACHMAN 1941 : Sensibilizaciones a hongos en la Ciudad 

de Buenos Aires (Anal. Inst. Invest. Fisicas Patol. Humana 3: 189-194). 
& L. G. BONZART 1941: Pollenosis caused by allergic flora (Prensa Med. 

Argent. 28: 3451). 
& R. H. MOLFINO 1941: Investigaciones sober flora alergogena en la Re- 

publica Argentina (Anal. Inst. Invest. Fisic. Patol. Humana 3: 177-188). 
f & M. A. SOLARI 1940: Notas sober la flora alergogena de la 

region de Bahia Blanca (Prensa Med. Argent. 28(52) : 2688). 
MORROW, MARIE B., E. P. LOWE & HOMER K. PRINCE 1942: Mold fungi in the 

etiology of respiratory allergic diseases, I. A survey of airborne molds (/. Allergy 

13(3) : 215-226). 
MULLIN, W. V. 1922: Pollen and hayfever a regional problem (Trans. Amer. 

Acad. Ophthalmol. & Oto-LaryncjoL). 

1923 : Pollen and hayfever (Colo. Med. 20: 96). 

NEWELL, J. M. 1942: A review of the chemical studies on the allergens in pollens 

(/. Allergy 13 (1) : 177-203). 
NICHOL, E. S. & O. C. DURHAM 1931 : A pollen survey of Miami, Florida (South. 

M. J. 24: 947). 
PARLATO, S. J. 1928: Studies of the relative intensity of distribution of ragweed 

pollen during a period of three years (N. Y. State M. J. 28: 1095-1097). 
PATTERSON, P. M. & L. N. GAY 1932 : The pollen content of air and its relation to 

hayfever in Baltimore, Md. during 1930 (/. Allergy 3(3) : 282-295). 
PAYER, J. B. 1860: Legons sur les Families naturelles des Plantes (Paris). 
PENFOUND, W. T. & B. G. EFRON 1929: A standardized method for pollen air analy- 
sis (Proc. Soc. Exp. Biol. & Med. 27: 650-654). 
1 & j. J. MORRISON 1930: A survey of the herbaceous plants in 

New Orleans in relation to allergy (/. Allergy I: 369-374). 
PHILLIPS, E. W. 1922 : Treatment of hayfever with Arizona pollens (Southwestern 

Med. Apr. 9, 1922). 

1923: Hayfever in central Arizona (Southwestern Med. 7(8) : 273-281). 

1926: Relief of Hayfever by intradermal injections of pollen extract 

(/. Amer. Med. Assn. 86: 182-184). 
1928: Ragweed hayfever in Salt River Valley (Southwestern Med. 12: 

1930: Ragweed hayfever in Salt River Valley (Southwestern Med. 14: 


1932: Pollen incidence in central Arizona (/. Allergy 3(5) : 489-494). 

1939: Time required for the production of hayfever by a newly encoun- 
tered pollen, sugar beet (/. Allergy 11(1) : 28-31). 
1940: Time required for the production of hayfever by spores of a newly 

encountered fungus, Johnson grass smut (J. Allergy 12(1) : 24-27). 
PHILLIPS, MARIE E. 1941 : Studies in atmospheric pollen (The Med. J. Australia 

2: 189). 
PIEMEISEL, R. L. 1932: Weedy abandoned lands and the weed hosts of the beet leaf 

hopper (U. S. Dept. Agric. Circ. 229, 23 pp., 10 figs.). 
& F. R. LAWSON 1937: Types of vegetation in the San Joaquin Valley of 

California and their relation to the beet leaf hopper (U. S. Dept. Agric. Tech. Bull. 

557, 28 pp., 14 figs.). 
PINESS, GEORGE 1925 : A study of two hundred and two cases of hayfever (/. Amer. 

Med. Assn. 85: 584-587). 
& H. E. McMiNtf 1927: The role of the structural features of pollen 

grains in the identification of the most important hayfever plants in California 

(/. Lab. & Clin. Med. 12: 1164-1178). 
& HYMAN MILLER 1930: An unusual opportunity to make an allergic study 

of an entire community with the etiology and results of treatment (/. Allergy 

1: 117). 

Hayfever Plants 225 Bibliography 

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PIPER, C. V. 1906: Flora of the State of Washington (Washington, D. C). 

& R. K. BEATTIE 1914: Flora of Southeastern Washington and adjacent 

Idaho, 296 pp. (Pullman, Wash.). 

& 1915: Flora of the Northwest Coast (Lancaster, Pa.). 

POHL, FRANZ 1937: Die Pollenerzeugung der Windbliitler (Beihefte sum Dot. 
Centralbl. 56: 366-470). 

PRATT, H. N. 1938 : Seasonal aspects of asthma and hayfever in New England (New 
England J. Med. 219: 782-786). 


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225: 533). 

PRINCE, H. E. & MARIE B. MORROW 1937: Molds in the etiology of asthma and 
hayfever with special reference to the coastal area of Texas (/. So. Med. Assn. 
30(7): 754-762). 

& P. G. SECREST 1939: Immunologic relationship of giant, western, com- 
mon ragweed and marsh elder (Iva cillata} (J. Allergy 10(6) : 537-548). 

, W. A. SELLE & MARIE B. MORROW 1934: Molds in the etiology of asthma 

and hayfever (Texas State J. Med. 30: 340-344). 

PROCTOR, B. E. 1934: The microbiology of the upper air, I (Proc. Amer. Acad. Arts 
and Sci. 69(8) : 315-340). 

1935: The microbiology of the upper air, II (/. Bacterial 30(4): 363- 


RACKEMANN, F. M. 1931 : Clinical allergy, particularly asthma and hayfever. Mech- 
anism and treatment (New York, The Macmillan Co.)- 

& L. B. SMITH 1931a: The plant pollens of New England. Their relative 

importance (/. Allergy 2: 364-371). 

& 19316: The hayfever plants of eastern Massachusetts. A pre- 
liminary study (New England J. Med. 204: 708-710). 

RAMIREZ, M. A. 1930: Pyrethrum, etiologic factor in vasomotor rhinitis and asthma 
(/. Allergy 1: 149-155). 

REHDER, ALFRED 1940: Manual of Cultivated Trees and Shrubs Hardy in North 
America, 996 pp. (New York, Macmillan). 

REMPE, HELMUT 1937 : Untersuchungen iiber die Verbreitung des Bliitenstaubes 
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ROGERS, JULIA E. 1905: The Tree Book (New York). 

ROSENDAHL, C. O., R. V. ELLIS & O. A. DAHL 1940 : Air borne pollen in the Twin 
Cities area with reference to hayfever (Minnesota Med. 23: 619). 

1 & H. B. SWEETSER 1936: Symposium on hayfever (Minnesota 

Med. 19: 505-513). 

ROWE, A. H. 1928: A study of the atmospheric pollen and botanic flora of the east 
shore of San Francisco Bay (/. Lab. & Clin. Med. 13(5) : 416-439). 

1929: Botanical survey of San Francisco (Calif. & West. Med. 30: 173- 


1931: Botanical survey of San Joaquin County in central California (/. 

Allergy 3: 98). 

1932: Botanical survey of San Joaquin County in central California (/. 

Allergy 3(4): 375-388). 

1939: Pine pollen allergy (/. Allergy 10(4) : 377-378). 

& J. W. HOWE 1935: A botanical survey of northwestern California (/. 

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RYDBERG, P. A. 1916: Tribe 12, Anthemideae (North American Flora 34: 242-285). 

1917: Flora of the Rocky Mountains and Adjacent Plains, 1110 pp. (New 


1922: Ambrosiaceae (The North American Flora 33(1): 1-37). 

1932: Flora of the Prairies and Plains of Central North America (New 


SACK, S. & H. G. GOLAN 1942 : The relationship between clinical symptoms and pol- 
len count in pollinosis (/. Allergy 13(3) : 296). 

Roger P. Wodehouse 226 Hayfever Plants 

ST. JOHN, HAROLD 1937: Flora of Southeastern Washington and Adjacent Idaho 

(Pullman, Washington). 

SARGENT, C. S. 1897: Silva of North America, 14 vols., 2185 pp., 740 pis. (Cam- 
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1922: Manual of the Trees of North America (Exclusive of Mexico), 910 

pp., 780 figs. (Cambridge, Mass.). 

SAVAGE, D. A. 1935: They came through (Soil Conservation 1(2) : 4-5). 
. 1937: Drought survival of native grass species in the central and southern 

Great Plains, 1935 (U. S. Dept. Agric. Tech. Bull. No. 549: 1-51). 
SCHEPPEGRELL WM. 1916(j : Hayfever in the southern states (So. Med. J. 9: 614- 

\9l6b: Hayfever: its cause and prevention (/. Amcr. Mcd. Assn. 66(10) : 

1917a: Hayfever. Its cause and prevention in the Rocky Mountain and 

Pacific states (U. S. Pub. Health Repts., Reprint 412: 1135-1152). 
19176: The classification of hayfever pollens from a biological standpoint 

(Bost. Med. & Surg. J. 177: 42-50). 
1920: The seasons, causes and geographical distribution of hayfever and 

hayfever resorts in the United States (U. S. Pub. Health Rcpts., No. 610, 35(39) : 

1922: Hayfever and Asthma, 274 pp., 108 figs. (Philadelphia, Lea & 

Febiger) . 
1923a: The immunological classification of common hayfever plants and 

trees (M. J. & Rec. (New York) 117: 721-726). 
19236: Analysis of six annual seasons of fall hayfever in New Orleans 

(U. S. Pub. Health Repts. 38: 1565). 

1925: Tree pollen hayfever (New Orleans Med. & Surg. J. 78: 132-136). 

SCHONWALD, PHILIPP 1937: Atmospheric causes of allergy in Washington (North- 
west. Med. 36(1) : 14-18). 
SCHWARTZ, Louis & L. H. WARREN 1940 : Dermatitis caused by contact with cop- 

perweed (Oxytenia acerosa Nutt.) (/. Allergy 12(1) : 63-68). 
SCOTT, E. B., L. H. CRIEP M. A. GREEN 1936: Pollen survey in Pittsburgh, Pa. 

(/. Allergy 7(1) : 80-85). 
SELFRIDGE, G. 1918: Spasmodic vasomotor disturbances of the respiratory tract with 

special reference to hayfever (Calif. State J. Med. 16: 164). 
1919: Endocrine glands and their relation to vasomotor disturbances, 

hayfever and asthma, with the past year's report (Calif. State J. Med. April-May, 


1920: Vaso-motor disturbances of the nose with special reference to hay- 
fever with a report for the year of 1919 (The Laryngoscope 30(10) : 611-625). 
SELLERS, E. D. 1929: Mesquite tree pollen as a cause of hayfever (Tex. State J. 

Med. 25: 297-299). 
1934: Hayfever pollens of the west Texas area (Tex. State J. Med. 30: 


1935: Pollinosis in the Southwest (So. Med. J. 28(8) : 710-714). 

& W. B. ADAMSON 1932: A study of the apparent atopic similarity 

of certain Chenopodialcs pollens (/. Allergy 3(2) : 166-171). 
SERVICE, W. C. 1934: Hayfever of Pikes Peak region (Colo. Med. 31: 311-313). 
SHANTZ, H. L. & R. L. PIEMEISEL 1924 : Indicator significance of the natural vege- 
tation of the southwestern desert region (/. Agric. Res. 28(8) : 721). 
SHELMIRE, BEDFORD 1939 : Contact dermatitis from weeds : patch testing with their 

oleoresins (/. Amer. Med. Assn. 113: 1085-1090). 

1940: Contact dermatitis from vegetation (So. Med. J. 33(4) : 337-346). 

SINNOTT, E. W. 1935: Botany. Principles and Problems, 525 pp., 310 figs. (New 

York, The McGraw-Hill Co.). 
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1933: Manual of the Southeastern Flora (New York). 

SPITZ, HERMAN 1927: Pollen sensitization (/. Tenn. M. A. 20: 78-81). 

Hayfever Plants 227 Bibliography 

STANTON, T. R. 1929: Oats in the north-central states (U. S. Dept. Agric. Farmer's 

Bull. No. 1581). 
STEALY, CLAIR L. 1936: The pollen content of the air of San Diego, Calif. (/. Lab. 

6- din. Med. 22: 273). 

STEMEN, T. R. & W. S. MYERS 1937: Oklahoma Flora (Oklahoma City). 
STIER, R. F. E. & G. L. HOLLISTER 1926 : Hayfever ; results of treatment with pollen 

extracts (Northwest Med. 25(12) : 655-658). 
f & T. A. BONSER 1930: A botanical survey of the hayfever-pro- 

ducing plants in the Pacific Northwest (/. Allergy 1(3) : 260-281). 
STOSSER, A. V. 1942: Recent observations on hayfever in children (Med. World 

60(10) : 459-462). 
STROH, J. 1940: Flora and pollen surveys of Seattle and vicinity (Northwest Med. 

39: 258). 

STULL, ARTHUR, R. A. COOKE & J. H. BARNARD 1936: The biologic identity of cer- 
tain grass pollens causing hayfever (/. Allergy 3(4) : 352-356). 
SULZBERGER, M. B. & C. B. WsiNBERG 1930: Dermatitis due to insect powder 

(/. Amer. Med. Assn. 95(2) : 111-112). 
SWINEFORD, OSCAR JR. 1940: Catalpa as a cause of hayfever (/. Allergy 11(4): 

SWINGLE, DEANE B. 1934: A Textbook of Systematic Botany, 270 pp., 76 figs. 

(New York). 
SYLVESTER, C. B. 1939a: Ragweed survey in Maine for 1938 (Maine Med. J. 30: 97). 

19396: Ragweed in Australia (/. Allergy 10(5) : 512). 

& O. C. DURHAM 1938: Ragweed pollen survey in Maine for 1937 (Maine 

Med. J. 29: 261-266). 
TEMPLETON, H. J. 1924 : Hayfever in the Sonoran belt of the Intermountain District 

(Calif, and Western Med. 22: 317-320). 
TER HEEGE, F. H. 1941 : Tropical hayfever (Geneesk. Tijdschr. v. Nederl-Indie 

81: 123). 

THARP, B. C., University of Texas, 1937. Personal communication. 

1934: Trees for street ornamentation (New Orleans M. & S. J. 86: 666). 

& G. H. HAUSER 1931 : The value of atmospheric pollen plates in hayfever 

and asthma (So. M. J. 24(12) : 1049-1053). 

TIIOMMEN, A. A. 1930: Hayfever: the spring type (Med. J. & Rec. 131: 496). 
1931 : Hayfever. Pt. 3 of "Asthma and Hayfever in Theory and Practice" 

by A. F. COCA, M. WALZER & A. A. THOMMEN (Springfield, 111., C. C. Thomas). 
TIDESTROM, IVAR 1925: Flora of Utah and Nevada (U. S. Dept. Agric. Contrib. 

U. S. Nat. Herbarium 25). 
TODD L. C. 1934 : Hayfever pollen content of air in Charlotte, N. C. 1933 (So. Med. 

& Surgery 96(7) : 343-346). 

TUFT, Louis 1942: Specific treatment of hayfever (/. Pediatrics 21(1) : 114-115). 
& G. I. BLUMSTEIN 1937: Incidence and importance of tree pollen hayfever 

with particular reference to Philadelphia and vicinity (/. Allergy 8: 464). 
VANDER VEER, A. JR., R. A. COOKE & W. C. SPAIN 1927 : Diagnosis and treatment 

of seasonal hayfever (Amer. J. Med. Sci. 174: 101-113). 
et al. 1942: Report of the Committee on a pollen survey of the United 

States. The Society for the Study of Allergy and allied conditions (/. Allergy 

13(5) : 516-527). 
VAUGHAN, W. T. 1931 : Allergy and Applied Immunology (St. Louis, C. V. Mosby). 

1939: Practice of Allergy, 1082 pp., 338 figs. (St. Louis, C. V. Mosby). 

W. R. GRAHAM & RUTH W. CROCKETT 1933: Hayfever pollen prevalence 

in Virginia: Review of a six years' survey (Va. M. Monthly 60: 158-162). 
WALDBOTT, G. L. & W. C. STEERE 1931 : Survey of the hayfever situation of Detroit 

(/. Detroit Coll M. 6- S. 2: 3-9). 
WALKER, H. & R. F. CARR6N 1940 : A contribution to the study of pollinosis in the 

Argentine Republic. A new plant allergen, Celtis tala (Dia Med. 1940 (6) : 140-1). 
WALKER, I. C. 1921 : Frequent causes and treatment of seasonal hayfever (Arch. 

Int. Med. 28: 71-118). 
WALTON, C. H. A. 1939: Pollen disease, report of 111 cases (Manitoba Med. Rev. 

June 1939). 
1940: Pollen disease in western Canada (Can. M. A. J. 42: 63). 

Roger P. Wodehouse 228 Hayfever Plants 

& M. G. DUDLEY 1940: Pollen survey in Manitoba (Con. M. A. J. 42: 

WARING, J. J. 1925 : A hayfever plant survey of the city and county of Denver 

(Colo. Med. 22: 194-199). 
1926 : Report of the Hayfever Research Committee of the State Historical 

and Natural History Society of Colorado (Denver). 

& MAXY POPE 1927: The cotton of the cottonwood tree a factor in hay- 
fever (Colo. Med., July 1927). 

WATRY, ALVA & R. W. LAMSON 1931 : A botanical survey of Needles, Calif. (/. Al- 
lergy 2: 272-281). 
& 1934: The probable etiology of pollinosis in Gallup, New 

Mexico (/. Allergy 5(2) : 166-182). 
WATSON, S. H. & C. S. KIBLER 1922: Etiology of hayfever in Arizona and the 

Southwest (/. Amer. Med. Assn. 78: 719-722). 
WEIL, C. K. 1931 : Plants causing hayfever in Alabama (/. Med. Assn. Alabama 

1: 15-19). 

1937: Hayfever in Alabama (J. Med. Assn. Alabama March-April, 1937). 

1940: Summer hayfever of unknown origin (/. Allergy 11(4) : 361-372). 

WILLIS, A. H. & H. E. DEGLER 1939: Air conditioning for the relief of cedar pollen 

hayfever (Univer. Tex. Pub. No. 3932). 
WILLIS, J. C. 1908: A manual and dictionary of the flowering plants and ferns 

(Cambridge University Press). 
WILMER, H. B. & H. M. COBE 1932: A note on the quantitative survey of pollen 

(/. Allergy 3: 63-68). 
WILSON, R. A. 1934: Some hayfever problems in the Southwest (Southwestern 

Med. 18: 46-51). 
WODEHOUSE, R. P. 1926: Pollen grain morphology in the classification of the Anthe- 

mideae (Bull. Torrey Bot. Club 53: 479-485). 
1928a: The phylogenetic value of pollen grain characters (Ann. Bot. 42: 

19286 : Pollen grains in the identification and classification of plants, I. 

The Ambrosiaceae (Bull. Torrey Bot. Club 55: 181-198). 
l92Sc: Pollen grains in the identification and classification of plants, II. 

Barnadesia (Bull. Torrey Bot. Club 55: 449-462). 
1929a: Pollen grains in the identification and classification of plants, III. 

The Nassauvinae (Bull Torrey Bot. Club 56: 123-138). 
1929&: Pollen grains in the identification and classification of plants, IV. 

The Mutisieae (Amer. J. Bot. 16: 297-313). 
1929c: The origin of symmetry patterns of pollen grains (Bull. Torrey 

Bot. Club 56: 339-350). 
1930: Pollen grains in the identification and classification of plants, V. 

Haplopappus and other Astereae; the origin of their furrow configurations (Bull. 

Torrey Bot. Club 57 : 21-46) . 
1931 : The origin of the six -furrowed configuration of dahlia pollen grains 

(Bull. Torrey Bnt. Club 57: 371-380). 

1933: Atmospheric pollen (J. Allergy 4: 220-227). 

1935: Pollen Grains. Their structure, identification and significance in 

science and medicine, 574 pp., 123 figs., 14 pis. (New York, McGraw-Hill Co.). 

1939: Weeds, waste and hayfever (Natural History 43(3) : 150). 

1941 : The hayfever plants of the South (So. Med. J. 34(9) : 986-993). 

1942a: The ragweeds (International Correspondence Club of Allergy 5: 

1942&: Atmospheric pollen (Aerobiology. Pub. A. A. A. S. 17: 8-31, 

pi. MO). 

WOLF, J. G. 1924: Hayfever in Pueblo, Colo. (Colo. Med. 21: 163-167). 
WOOTON, E. O. & P. C. STANDLEY 1915 : Flora of New Mexico (Contrib. U. S. Nat. 

Herbarium 19). 
ZIVITZ, NELSON 1942: Allergy to Australian pine (Casuarina) (7. Allergy 13(3): 



ABRAMS, L. R., 17, 144, 146, 147, 149, 195, 

196, 197, 218 

Adamson, W. B., 96, 195, 226 
Albert, H M 200, 218 
Anderson, J. M., 157, 163, 206, 207, 208, 


Annand, P. N., 14, 218 
Aquarone, Paul, 170, 171, 218 
Ascher, M. S., 125, 218 
Atwood, Alice, 19, 219 

BAAGOE, K. H., 223 

Babb, M. F., 105, 218 

Bachman, A. E., 224 

Bailey, L. H., 15, 18, 218, 222 

Ball, C R., 62, 64, 218 

Balyeat, R. M., 91, 100, 175, 179, 182, 214, 


Barnard, J. H, 37, 227 
Barrett, Chas. E., 104, 163, 206, 207, 208, 


Bates, L. F., 178, 221 
Bayles, B. B., 45, 219 
Beattie, R. K., 18, 225 
Bentham, George, 128, 129, 131, 218 
Berger, W., 223 
Bernstein, T. B., 221 
Bernton, Harry S., 90, 126, 169, 170, 171, 


Bessey, C. E., 130, 218 
Biederman, J. B., 110, 150, 218 

Black, J. H., 29, 182, 218 

Blake, S. F., 17, 19, 219 

Blanton, W. B., 174, 219 

Blomquist, H. L., 173, 219 

Blumstein, G. I., 116, 126, 127, 166, 219, 

Bonser, T. A, 163, 203, 207, 227 

Bonzart, L. G., 224 

Bowen, Ralph, 186, 219 

Bowie, Evangeline, 183, 219 

Briggs Jr., L. J., 223 

Brink, R., 115, 219 

Britton, N. L., 16, 17, 19, 131, 219 

Broadkey, M. H., 91, 224 

Brown, Addison, 16, 17, 131, 219 

Brown, Grafton Tyler, 77, 85, 111, 169, 
171, 219 

Carron, R. F., 90, 219, 227 
Castellani, A., 219 
Castex, M. R., 219 
Chafee, F. H., 169, 225 
Chamberlain, C. T., 48, 125, 197, 202, 203, 

Clapp, W. B., 69, 225 

Clark, Anna, 173 

Clark, J. A., 45, 219 

Clements, F. E., 19, 105, 106, 108, 153, 155, 

157, 158, 159, 161, 222 
Cobe, H. M., 168, 219, 227 
Coca, A. F., 227 
Cocke, Elton C., 12, 13, 174, 219 
Coles, J., 177, 219 
Colmes, A., 169, 225 
Cooke, R. A., 37, 168, 227 
Cooper, D. C., 115, 219 
Corradi, L. G., 219 
Coulter, J. M., 17, 64, 219 
Coville, F. C., 19 
Cowgill, H. B., 220 
Cranwell, Lucy M., 220 
Criep, L. H., 167, 168, 226 
Crockett, Ruth W., 173, 227 
Cromwell, H. W., 139, 220 
Cunningham, T. D., 136, 220 
Curtis, H., 28, 86, 221 

DAHL, A. O., 214, 220, 225 

Darlington, H. D, 139, 220 

Darwin, C., 21 

Davison, H. M., 22, 34, 181, 182, 220 

Deamer, W. C., 113, 200, 203, 220 

DeBell, V,, 200, 218 

Degler, H. E., 27, 228 

Denny, E. R., 183, 220 

Derbes, V. J., 116, 220 

Detweiler, H. K., 177, 220 

Dudley, M. G., 214, 228 

Duke, W. W., 89, 174, 209, 211, 212, 213, 

214, 220 
Durham, O. C, 22, 34, 91, 103, 136, 144, 

149, 150, 169, 174, 176, 177, 178, 181, 

182, 184, 209, 212, 213, 218, 220, 221, 

223, 224, 227 
Dutton, L, O., 101, 221 

EFRON, B. G., 57, 179, 183, 185, 186, 187, 

221, 224 
Ellis, R. V., 59, 115, 154, 157, 160, 211, 

212, 213, 214, 220, 221, 225 
Emerson, A. J., 19, 221 
Erdtman, G., 9, 10, 19, 221 

FASSETT, N. C., 178, 221 

Faxon, C. E., 19 

Feinberg, S. M., 13, 136, 149, 176, 178, 221 

Fernald, M. L,, 16, 141, 169, 221, 222 

Figley, K. D., 177, 221 

Firbas, F., 221 

Flint, C. L., 221 

itoger r. woaenouse 

nayiever riants 

Foerste, A. F., 142, 221 
Foskett, H. H., 115,221 
Foss, A. R., 208, 221 
Fox, E. C, 114, 221 
Freeman, J., 221 
French, S. W., 185, 221 
Freud, E. M., 168, 221 
Fromer, J., 169, 225 

GARRETT, A. O., 221 

Gates, F. C., 17, 211, 221 

Gay, L. N., 28, 86, 171, 218, 221, 223, 224 

Geddes, W. N., 142, 221 

George, E. J., 89, 124, 221 

Gill, Mary W., 19 

Gleason, H. A., 151, 222 

Golan, H. G., 15, 225 

Goldstein, M. B., 152, 222 

Goltman, A. M., 179, 181, 183, 223 

Graham, Evelyn, 223 

Graham, W. R., 173, 227 

Gray, Asa, 16, 131, 222 

Greco, J. A., 222 

Green, M. A., 167, 168, 226 

Greene, J. E., 169, 225 

Greenhouse, C A., 152, 222 

Griffiths, David, 53, 222 

Griscom, Ludlow, 141, 221 

Groh, H., 178, 222 

Grothaus, E. M., 27, 28, 179, 183, 185, 223, 

Gutmann, M. J., 222 

HALL, H. M., 19, 83, 84, 102, 105, 106, 108, 
111, 113, 146, 153, 155, 157, 158, 159, 
161, 195, 197, 201, 202, 222 

Hansel, F. K., 169, 171, 178, 214, 222 

Kara, H. J., 222 

Harsh, G. F., 136, 222 

Hauser, G. H., 184, 227 

Hawes, R. C., 14, 222 

Heinberg, C. J., 179, 222 

Henry, J. P., 183, 222 

Herring, A. L., 183, 222 

Hitchcock, A. S, 16, 17, 19, 37, 45, 52, 54, 

Hoch, J. H., 174, 222 

Hodgson, H., 28, 168, 222 

Hollister, G. L., 163, 203, 207, 227 

Hooker, J. D., 131, 218 

Hough, R. B., 19, 222 

Howe, J. W., 102, 201, 203, 225 

Howell, Thomas, 18, 222 

Huber, Harry L., 136, 176, 222 

Hulsey, S., 185, 222 

Hurst, Helena, 177, 220 

Hurwitz, S. H., 222 

JAMIESON, C. A., 115, 223 
Jamieson, H. C., 223 

Jenkins, H. L., 203, 220 
Jepson, W. L., 18, 19, 223 
Johnson, R. P., 209, 223 
Jones, K. L., 141, 223 

KAHN, I. S., 27, 28, 114, 132, 179, 183, 

185, 223, 227 
Kearney, T. H., 17, 223 
Kelly, J. W., 7, 223 
Key, S. N., 27, 184, 223 
Kibler, C. S., 108, 146, 150, 190, 191, 193, 

194, 228 
Koessler, K. K., 176, 223 

LACKEY, J. B., 179, 181, 183, 223 

Lambert, E. B., 218 

Lamson, R. W., 62, 96, 123, 190, 191, 194, 

195, 197, 223, 228 
Langley, W. D., 151, 223 
LaRush, Florence, 177, 178, 223 
Lawson, F. R., 102, 204, 224 
Lazarus, Dorothy S., 203, 220 
Lee, A. B., 9, 223 

Lewis, I. M., 19, 223 

Lindau, Walter, 223 

Linnaeus, C., 141 

Little, D. M., 218 

Lockhart, W. M., 218 

Lowance, M. L, 22, 34, 181, 182, 220 

Lowe, E. P., 186, 224 

Liidi, Werner, 223 

Lyomret, P., 223 

MCGARY, L., 178, 221 

McLean, J. W., 223 

McMichael, H., 223 

McMinn, H. E., 113, 197, 200, 220, 223, 

224, 225 

MacQuiddy, E. L., 213, 223 
Mallen, M. S., 223 
Maloney, E. S., 91, 224 
Malvarez, H. E., 90, 219 
Mease, James, 52 
Metzger, F. C., 182, 184, 224 
Miller, Hyman, 14, 197, 222, 224, 225 
Millspaugh, C. F., 19, 147, 224 
Minshall, W. H., 178, 222 
Molfino, R. H., 219, 224 
Moore, Mar j one, 139, 220 
Moreno, G. Ruiz, 219, 224 
Morrison, J. J., 57, 179, 183, 224 
Morrow, Marie B., 186, 224, 225 
Mullin, W. V., 208, 224 
Myers, W. S., 17, 227 

NELSON, AVEN, 17, 64, 219 
Newell, J. M., 224 
Nichol, E. S., 150, 182, 184, 224 
Norris, T., 28, 86, 221 

Hayfever Plants 


Author Index 

Costing, H. J., 173, 219 

PARLATO, S. J., 224 

Patterson, P. M., 171, 224 

Payer, J. B., 131, 224 

Peebles, R. H., 17, 223 

Penfound, W. T., 57, 179, 183, 224 

Phillips, E. W., 101, 121, 146, 147, 149, 190, 

191, 192, 193, 194, 224 
Phillips, Marie E., 224 
Piemeisel, R. L., 102, 204, 223, 224, 226 
Piness, George, 102, 197, 202, 224, 225 
Piper, C. V., 18, 225 
Pohl, Franz, 6, 225 
Pope, Maxy, 208, 209, 228 
Potts, George, 201 
Pratt, H. N., 169, 225 
Prince, H. E, 34, 133, 139, 186, 224, 225 
Proctor, B. E., 218, 225 


RACKEMANN, F. M., 167, 168, 169, 225 

Ramirez, M. A., 152, 225 

Rasmussen, 61 

Render, Alfred, 18, 66, 225 

Rempe, Helmut, 9, 225 

Rinkel, H. J., 91, 182, 218 

Robinson, B. L., 16, 222 

Rogers, Julia E., 19, 225 

Rosendahl, C. O., 59, 115, 154, 157, 160, 

211, 212, 213, 214, 221, 225 
Rowe, A. H., 22, 38, 102, 105, 113, 147, 155, 

159, 160, 197, 199, 200, 201, 202, 203, 

Rydberg, P. A., 17, 19, 132, 139, 144, 153, 

155, 161, 212, 213, 225 

SACK, S., 15, 225 

St. John, Harold, 18, 226 

Sargent, C. S., 18, 64, 66, 81, 226 

Savage, D. A., 54, 226 

Scheppegrell, Wm., 12, 13, 48, 89, 122, 132, 

146, 179, 183, 195, 197, 201, 202, 226 
Schonwald, Philipp, 203, 226 
Schwartz, Louis, 135, 226 
Scott, E. B., 167, 168, 226 
Secrest, P. G., 133, 139, 225 
Selfridge, G., 45, 137, 149, 155, 197, 201, 

202, 226 

Selle, W. A., 186, 225 
Sellers, E. D., 34, 96, 114, 190, 191, 195, 


Service, W. C., 204, 206, 207, 208, 209, 226 
Shantz, H. L., 102, 226 
Shelmire, Bedford, 226 
Sherff, E. E., 19, 147, 224 

Sinnott, E. W., 16, 226 

Small, James, 130, 226 

Small, John K., 16, 17, 131, 226 

Small, W. S., 14, 222 

Smith, L. B., 167, 168, 225 

Solari, M. A., 219, 224 

Spain, W. C., 168, 227 

Spitz, Herman, 183, 226 

Stahl, H. S., 173 

Standley, P. C, 17, 222, 228 

Stanford, E. E., 202 

Stanton, T. R., 48, 227 

Stealy, Clair L., 197, 227 

Steere, W. C., 177, 227 

Steinberg, M. J., 13, 221 

Stemen, T. R., 17, 100, 175, 179, 182, 218, 


Stickler, M., 223 

Stier, R. F. E., 163, 203, 207, 227 
Stosser, A. V., 214, 227 
Stroh, J., 203, 227 
Stull, Arthur, 37, 227 
Sulzberger, Marion B., 152, 222, 227 
Swallen, J. R., 17 
Sweetser, H. B., 225 
Swineford Jr., Oscar, 227 
Swingle, Deane B., 15, 16, 227 
Sylvester, C B., 169, 227 

TEMPLETON, H. J., 204, 208, 227 

Tenny, G. E., 183, 220 

Tennyson, Alfred, 61 

Ter Heege, F. H., 227 

Tharp, B. C., 27, 227 

Thiberge, Narcisse, 179, 184, 227 

Thommen, A. A., 52, 89, 168, 169, 178, 227 

Thornber, J. J., 193 

Tidestrom, Ivar, 17, 227 

Todd, L. C., 174, 227 

Tuft, Louis, 126, 127, 166, 219, 227 

Tupinamba, A., 222 

VANDER VEER JR., A., 168, 227 
Vareschi, Volkmar, 223 
Vaughan, W. T., 169, 171, 173, 178, 197, 
214, 227 

WALDBOTT, G. L., 177, 227 

Walker, H., 90, 227 

Walker, I. C., 22, 37, 168, 227 

Walton, C. H. A., 214, 227, 228 

Walzer, M., 227 

Waring, J. J., 174, 207, 208, 209, 222, 228 

Warren, L. H., 135, 226 

Watry, Alva, 62, 123, 190, 191, 194, 195, 

197, 223, 228 
Watson, S. H., 108, 146, 150, 190, 191, 193, 

194, 197, 202, 228 

Roger P. Wodehouse 


Hayfever Plants 

Weed, C M., 19, 221 
Weil, C. K., 179, 183, 185, 228 
Weinberg, C. B., 152, 227 
Wells, W. F., 10, 11, 218 
Willis, A. H., 27, 228 
Willis, J. C, 16, 228 
Wilmer, H. B., 168, 228 
Wilson, R. A., 189, 194, 228 

Wodehouse, R. P., 7, 14, 68, 100, 115, 121, 
132, 135, 142, 151, 154, 163, 168, 182, 
218, 228 

Wolf, J. G., 208, 228 

Wolfe, A. M., 136, 220 

Wooton, E. O., 17, 228 

Wulff, Thorold, 61 

ZIVITZ, NELSON, 81, 182, 228 


Bold type indicates references, asterisks illustrations 

Abele, 64 

Abies, 25 

Abietineae, 21 

Abilene, Texas, 190 

Absinth sage, 158 

Acacia, 111, 197, 113 

Acacia pollen, 112* 

Acanthoxanthum, 147, 149 

Acer, 116, 118*, 119*, 120*, 166 

Acer ace ae, 116 

Acer in the North Pacific States, 199 

Acer in the Rocky Mountain States, 206 

Acer pollen, 112* 

Achillea, 152 

Acnida, 99*, 179, 207 

Adirondack Mountain region, 169 

Aerosol collector, 9, 10* 

African daisy, 150 

Agropyron, 44, 167 

Agrostideae, 48 

Agrostis, 50*, 51 

Ailanthus, 115 

Ailanthus family, 115 

Ailanthus pollen, 129* 

Air filtration method of collecting pollen, 


Aiten, 27 

Alabama, 178, 183 
Albiszia, 114 
Alder, 67, 71 
Alder flowers, 71* 

Alder in the North Pacific States, 199 
Alder pollen, 69* 
Alder, black, 71 
hoary, 71 

Oregon, 199 

red, 199 

Sitka, 71 

smooth, 71 

speckled, 71 

tag, 71 

thin-leaved, 199 

wavy-leaved, 71 

white, 72 

Alfalfa, 115 

Algaroba, 113 

Alkaliblite, 102 

Alkali grass, 43 

Allenrolfia, 101,206 

Allergenic toxicity, 6 

Allscale, 108 

Alnus, 71 

Alnus flowers, 71* 

Alnus in the North Pacific States, 199 

Alopecurus, 48, 167, 206 
Alternaria, 186, 187 
Amaranth, 96 
globe, 96 

green, 97 

spiny, 99, 175, 179, 191 

spleen, 96, 98 

tassel, 96 

Amaranthaceae, 95 
Amamnthus, 96, 97*, 98*, 179 
Atnaranthus in the Rocky Mountain 

States, 207 

Amaranthus in the Southwest, 191 
Atnaranthus pollen, 95* 
Ambrosia, 137, 140*, 141*, 143* 
Ambrosia, classification of, 132 
Ambrosia flowerheads, 137* 
Ambrosia in the North Pacific States, 201 
Ambrosia in the Southern States, 181 
Ambrosia in the Southwest, 192 
Ambrosia pollen, 129* 
Ambrosia seedling, 31* 
Ambrosia seeds, 138 
Ambrosieae, 132 
Ambrosineae, 133 
Ammophila, 51 
Amphiphilous flowers, 4 
Anaphilis, 150 
Andropogon, 58 
Andropogoneae, 58 
Anemophilous flowers, 5 
Angiosperms, definition of, 30 
Annapolis Valley, Nova Scotia, 169 
Annual bluegrass, 41 
Antennaria, 150 
Anthemideae, 151 
Anthemis, 151 
Anther, 2 

Anthoxanthum, 54* 
Apple, 109, 110 
Arborvitae, 25 
Arctium, 162 
Arctotidae, 150 
Arecaceae, 34 
Arizona, 188 
Arkansas, 178 
Artemisia, 152*, 153, 156*, 157-160*, 161, 


Artemisia, hay fever species of, 154 
Artemisia in the North Pacific States, 201 
Artemisia in southern California, 195 
Artemisia in the Southern States, 181 
Artemisia in the Southwest, 193 
Artemisia pollen, 129* 

Roger P. Wodehouse 


Hayfever Plants 

Artichoke, globe, 162 

Artocarpaceae, 90 

Asclepias cornuti, 3, 4* 

Ash, 123, 176, 211 

Ash in the North Pacific States, 200 

Ash in the Southwest, 189 

Ash pollen, 111* 

Ash, Arizona, 124, 189 

desert, 124 

flowering, 190, 200 

green, 123, 124, 211 

leather-leaf, 124 

mountain, 124 

Oregon, 124, 200 

red, 124 

r white, 123 
Aspen, 64 

Aspen, large-toothed, 65*, 66 

quaking, 65*, 66 

trembling, 66 

Aspergillus, 186, 187 

Association of Allergists for Mycological 

Investigation, 186 
Aster, 150 

Aster, cultivated, 150 
Astereae, 150 
Aster tribe, 150 
Atmospheric pollen, 8 
Atmospheric pollen slide, 8* 
Atriplex, 104, 107*, 192, 200, 207 
Atriplex in southern California, 195 
A triplex pollen, 95* 
Atriplex, sea-beach, 105 
Australian pine, 81, 182 
Aveneae, 47 

Baccharis, 150, 182 
Bahama grass, 51 
Balm of gilead, 66 
Barley, 45 
Barley, foxtail, 206 
Barley grass, 45 
Barley, meadow, 206 

mousear, 206 

Barnadesia, 163 
Barnadesia pollen, 130 
Basswood, 116 

Bay berry, 86 
Bayberry family, 86 
Beachgrass, 51 
Beachgrass, European, 51 
Beach sandbur, 147 
Bearded darnel, 45 
Beech, 75 

Beech, American, 76 
Beech pollen grain, 69* 
Beet, 101 
Beet, sugar, 101 
Bellis, 150 

Belvedere, 102 

Bent grass, colonial, 51 

creeping, 51 

metropolitan, 51 

velvet, 51 

Washington, 51 

Bermuda grass, 51, 52*, 171, 173, 175 

Beta, 101 

Bethlehem, New Hampshire, 169 

Betula, 68, 167, 179 

Betulaceat, 67 

Betula flowers, 68* 

Betula in the North Pacific States, 199 

Betula in the Plains and Prairies, 290 

Blloxi, Mississippi, 187 

Birch, 67, 68, 170, 176, 177, 179 

Birch in the North Pacific States, 199 

Birch in the Plains and Prairies, 209 

Birch pollen grains, 69* 

Birch, black, 70 

canoe, 70, 209 

cherry, 70 

gray, 70, 209 

low, 209 
paper, 70, 209 

red, 70, 209 

river, 70 

spring, 199 

water, 70 

white, 68*, 70, 199 

yellow, 70 
Blackberry, 109 
Black-eyed-susan, 131 
Black sage, 161 
Black walnut, 83 

Black walnut, California, 83 
Blazing star, 151 
Bluebeech, 67, 72 
Bluebeech catkins, 72* 
Bluebeech pollen, 69* 
Bluegrass, 40 

Bluegrass in the Southwest, 191 
Bluegrass, Canada, 167 

rough, 42 

Bluejoint grass, 44 
Bluestem, 44, 206 
Bog myrtle, 86 
Boneset tribe, 151 
Botanical literature, 15 
Bouteloua, 53, 190, 206 
Bow-wood, 91 

Boxelder, 120*, 166, 199, 206 
Bractscale, 106 
Bridal wreath, 109, 110 
Brome, downy, 191 
Brome grass, 38, 191, 206 
Bromus, 38, 191, 206 
Broomcorn, 58 
Broussonetia, 90, 170, 182 

Hayfever Plants 


General Index 

Broussonetia pollen, 95* 

Brunswick Beach, Georgia, 187 

Buchloe, 53 

Buckwheat, 92 

Buckwheat family, 92 

Budbrush, 161, 201 

Budsage, 161 

Buffalo grass, 53 

Buffalo grass formation, 53 

Bulbilis, 53 

Bull grass, 56 

Burdock, 162 

Burning bush, 102, 206 

Bur ragweed, 145, 175, 192, 195 

Bur ragweed flower heads, 149* 

Burroweed, 101, 147, 206 

Bur sage, Arizona, 146 

desert, 147, 196 

Sonora, 147 

Burweed, 135 

Burweed marshelder, 136, 175 
Bush sandbur, 193 
Buttercup flower, 1* 
Butternut, 83* 
Button-ball, 110 
Button-wood, 110 

Caesalpiniaceae, 111 

Calendula, 150 

Calendula tribe, 150 

Calenduleae, 150 

California, northern, 197 

California, southern, 195 

Call '1st ephus, 150 

Calyx, 1* 

Campestris group (Artemisia), 159 

Canada bluegrass, 41 

Canaigre, 94 

Canary grass, Mediterranean, 55 

reed, 55 

Candleberry, 86 
Cannabinaceae, 91 
Cannabis, 91, 213 
Cannabis pollen, 95* 

Canyon ragweed, 146, 147, 193 

Cape marigold, 150 

Capriola, 51 

Carduus, 162 

Carelessweed, 97*, 98, 135, 179, 191 

Carex, 59 

Carc.r pollen grains, 35* 

Carpels, 2* 

Carpet sage, 158 

Carpinus, 72*, 211 

Carya, 84, 170, 173, 179 

Carya pollen, 85* 

Cassie, 113 

Castanea, 75 

Castanopsis, 75 

Casuarina, 81, 182 
Casuarinaceae, 81 
Catabrosa, 206 
Cattail, 32, 33* 
Cattail pollen, 35* 
Cattail flag, 32 
Cedar, Carolina, 173 

incense, 25 

> Mexican, 27 
mountain, 27 

mountain, in the Southwest, 190 

red, 26 

rock, 27 

white, 25 

Celosia, 96 
Celtis, 89 
Celtis pollen, 85* 
Centaur ea, 162 

Central United States, floras of the, 17 

Chamaecy paris, 28, 200 

Chamomile, 151 

Chaparral tree, 87 

Chaptalia, 162 

Cheat, 38 

Cheat, sheathed, 191 

Chenopod, 103 

Chenopod family, 100 

Chenopodiaceae, 100 

Chenopodium 103, 104*, 176 

Cherry, 109, 110 

Chess, 38 

Chestnut, 75 

Chico, 102 

Chicory, common, 163 

Chicory tribe, 163 

Chinquapin, 75 

Chlorideae, 51 

Chloris, 191 

Chrysanthemum, 151 

Chrysanthemum Leucanthemunt, 151 

Chrysanthemum pollen, 129* 

Chufa, 60 

Cichorieat, 163 

Cichorium, 163 

Cirsium, 162 

Cladosporium, 186 

Cladothrix, 100 

Clotbur, beach, 213 

great, 148 

Clover, 115 

Clover, alsike, 115 

Dutch, 115 

honeysuckle, 115 

pink, 115 

purple, 115 

red, 115 

Cnicus, 162 

Coarse ragweed, 193 

COCKE'S formulae, 13 

Roger P. Wodehouse 


Hayfever Plants 

Cocklebur, 133, 147, 148*, 168, 171, 176 
Cocklebur in the Southern States, 181 
Cocklebur pollen, 129* 
Cocklebur, Pennsylvania, 148 
Cockscomb, 96 
Cocksfoot, 43 
Colorado, 204 
Colorado bluegrass, 44 
Colorado Springs, 206 
Committee of Allergists for the Study of 
the Unknown Causes of Hayfever, 186 
Compositae, 127 
Composite family, 127 
Composite flowers, 128* 
Coniferae, 21 
Copperweed, 132, 135 
Coral Gables, Florida, 187 
Cor chorus, 116 
Cord grass, 54 
Cornus florida, 3* 
Corolla, 1* 
Corylus, 74*, 178, 211 
Cosmos, 131 
Cottonwood, 64, 176 
Cottonwood in the North Pacific States, 

Cottonwood in the Rocky Mountain 

States, 205 

Cottonwood, Arizona, 67, 189 
black, 67 

California, 65*, 67 

Fremont's, 67 

mountain, 65*, 67, 189 

narrow-leaved, 67 

river, 66, 205 

Rydberg's, 67, 189 

smooth-barked, 67 

valley, 65*, 67, 189 

western, 65*, 205 

willow-leaf, 65*, 67, 205 

Couchgrass, 44 
Crabgrass, 56 

running, 56 

Crataegus, 109 
Crested hair grass, 48 
Crossostephmm, 154, 155 
Crowfoot grass, 56 
Cudweed, 157 

Cultivated plants, botany of the, 18 

Cupressineae , 25 

Cupressus, 25, 28 

Cyclachaena, 132, 135, 136*, 193 

Cyclachaena in the Southern States, 181 

Cyclachaena pollen, 129* 

Cycloloma, 101 

Cynara, 162 

Cynareae, 162 

Cynodon, 51, 52* 

Cyperaceae, 59, 60 

Cyperus, 59, 60 
Cypress, 25, 28 

Dactylis, 43* 179 

Dahlia, 131 

Daisy, African, 150, 162 

English, 150 

Natal, 162 

ox-eye, 151 

Dallis grass, 56, 171 
Dandelion, 163, 203, 208 
Dandelion pollen, 129* 
Danthonia, 167 
Darnel, 45 
Delaware, 169, 170 
Desert bursage, 193 
Desert holly, 105 
Desert sage, 108 

Dew grass, 43 
Dicroia, 132, 137, 193 
Dicotyledons, 31*, 60 
Dicotyledons, leaves of, 31* 
Digitaria, 56 
Dlmorphotheca, 150 
Dioecious, 2 
Dipteronia, 116 
Distichlis, 43, 191 
District of Columbia, 169, 170 
Dock, 92, 95*, 201 
Dock, bitter, 93, 212 

broad-leaved, 93 

curly, 93, 94* 

fiddle, 201 

field, 92 

great water, 212 

pale, 212 

peach-leaved, 212 

pie, 94 

red, 92 

sorrel, 92, 93*, 173 

sour, 94 

western, 201 

wood, 92 

Dog grass, 44 
Dogwood, 3* 
Dondia, 102 
Dover grass, 39 
Dragon sagewort, 159 
Durra, 58 

Eastern United States, 167 
Echinops, 162 
Egyptian millet, 58 
Eleocharis, 59 
Elm, 86, 87*, 166, 173, 176 
Elm in the Southern States, 182 
Elm pollen grain, 85* 
Elm, cedar, 89 

Chinese, 89 

Hayfever Plants 


General Index 

cork, 88 

dwarf, 89 

English, 89 

Florida, 88 

red, 89 

rock, 88 

Scotch, 89 

scrub, 89 

September, 89 

slippery, 88* 

white, 87* 

r winged, 88 

Encina, 80 
Endive, 163 

English bluegrass, 39, 41, 45 

English ryegrass, 45 

Entomophilous flowers, 2 

ERDTMAN, method of catching pollen, 9, 


Erigeron, 150 
Estafiata, 158 
Estragon, 159 
Eucalyptus, 200 
Eugene poplar, 66 
Eupatoricac, 151 
Eupatorium, 151 
Euphrosync, 132 
rof la/101 
EuxanthiMn, 147, 149 
Ever grass, 45 
Evergreen grass, 39, 58 

Fabaceae, 111, 114 

Fagaccae, 75 

Fagopyrum, 92 

Fagus, 75 

False ragweed, 133, 145, 147, 192, 201, 207 

False wheat, 44 

Feather grass, 191 

Fescue, 39 

Fescue, meadow, 39*, 167 

red, 39, 40*, 167 

sheep, 40 

Festuca, 39*, 40* 
Festuceae, 38 
Feverfew, 132 
Ficus, 90 

Field sagewort, 160* 

Filament, 2 

Filbert, 74 

Finger grass, 56, 191 

Fir, 25 

Fire bush, 102 

Fire bush, Mexican, 192 

Flat-stemmed meadow grass, 41 

Fleabane, 150 

Fleshscale, 106 

Florida, 178, 184 

Flower, the, 1* 

Forsythia, 121 

Franseria, 133, 145, 146*, 192, 201, 207, 


Franseria flower heads, 149* 
Franseria in southern California, 195 
Fraxinus, 123 

Fraxinus in the North Pacific States, 200 
Fraxinus in the Southwest, 189 
Fraxinus pollen, 112* 
French spinach, 105 
Fungi in hay fever in the Southern States, 

Fusarium, 186, 187 

Gaertncria, 145, 146 
Gaillardia, 150 
Galingale, 60 
Galveston, 187 
Garden scale, 105 
Garrya, 203 
Georgia, 178 
Gcrbera, 162, 178 
Gink go, 20 
Gink go pollen, 24* 
Glasswort, 102 
Glycerine jelly, 8 
Gnaphalium, 150 
Goldenbells, 121 
Goldenrod, 129*, 150, 168 
Goldenrod, noble, 150 

seaside, 150 

Gomphrcna, 96 
Goosefoot, 103 
Goosefoot family, 100 
Goosefoot, nettle-leaved, 103 

oak-leaf, 104 

Grama, 53, 190 

black, 53, 190 

blue, 53, 190 

hairy, 53 

mat, 206 

mesquite, 53 

purple, 190 

Rothrock, 53, 190 

sixweeks, 53, 190 

Granrincae, 34 
Grasses in hayfever, 36 
Grasses, pollen grains of, 35* 
Grass family, the, 34 

Grass flower, 36* 

Gravity method of catching pollen, 12 

Gray sage, 157, 193 

Greasebush, 133, 149, 193, 196 

Greasewood, 102 

Greasewood pollen, 95* 

Greenville, Maine, 169 

Groundsel, 161 

Groundsel bush, 150, 182 

Groundsel tribe, 161 

Roger P. Wodehouse 


Hayfever Plants 

Gulfport, Mississippi, 187 
Gum tree, 200 
Gymnosperms, the, 20 
Gymnosperms, pollen grains of, 24* 

Hackberry, 86, 89 

Hackberry pollen, 85* 

Hackberry, southern, 85*, 89 

Hackmatack, 27 

Hairy chess, 191 

Hard grass, 43 

Hardhack, 73, 110 

HA WES, SMALL, and MILLER apparatus, 


Hawthorn, 109 
Hayfever regions of the United States, 

Hayfever resorts of the Northeastern 

United States, 169 
Hayfever resorts of the Southern United 

States, 187 
Hayfever toxicity, 6 
Hayfever of unknown origin, summer, 


Hazel, 74, 178 , 
Hazel, American, 74 

beaked, 74 

California, 75 

Hazel flowers, 74* 
Hazelnut, 74 

Hazel pollen grain, 69* 
Helenieae, 150 
Helenium, 150 
Heliantheae, 131 
Helianthus, 132, 193, 201 
Helianthus pollen, 129* 
Helichrysum, 150 
Helminthosporium, 186 
Hemlock, 25 
Hemlock, cones of, 22* 
Hemlock pollen, 24* 
Hemp, 91, 176, 213 
Hemp family, 91 
Hemp pollen, 95* 
Herbarium specimens, 7, 15 
Herd's grass, 51 
Hickory, 84, 170, 173 
Hickory pollen, 85* 
Hickory, shag, 85 

shell-bark, 85 

High- water shrub, 133 
Holcus, 47*, 48, 58 
Hollyscale, 105 
Honey locust, 113 
Honey mesquite, 113 
Hop, 92, 176 
Hop-hornbeam, 73 
Hop-hornbeam catkins, 73* 
Hordeae, 44 

Hordeum, 45, 206 
Hormodendrum, 186, 187 
Hornbeam, 72 

American, 72* 

Horse savin, 27 

Horseweed, 135 

Huisache, 113 

Humulus, 92 

Hymenoclea, 133, 149, 193, 196 

Ibota privet, 129 

Idaho, 204 

Identification of pollen, 14 

Illinois, 174 

Imperfectly entomophilous flowers, 4 

Indiana, 174 

Indian corn, 58 

Indian grass, 182 

Indian hair tonic, 159 

Indian rice, 55 

Inula tribe, 150 

Inuleae, 150 

Iodine bush, 181 

Iowa, 174 

Iron weed, 151 

Ironweed tribe, 151 

Ironwood, 67, 72, 73 

Ironwood pollen, 69* 

Iva, 132, 133*, 134*, 168, 176, 201 

Ira in the Southwest, 193 

Ivcneae, 132 

Ivray, 45 

Jacksonville Beach, Florida, 187 

Jasmin, 121 

Jasminum, 121 

Jecote, 193 

Jerusalem oak, 103, 176 

Joe-pye-weed, 151 

Johnson grass, 57*, 58, 190 

Joint-fir, 81 

Juglandaceac, 81 

Juglans, 82*, 83* 

Juglans in the North Pacific States, 199 

Juglans pollen, 85* 

Juncaceae, 60 

Juncoides, 60 

June grass, 41, 42* 167, 174 

June grass in the Southwest, 191 

Juniper, 25, 26, 173, 178 

Juniper in the Rocky Mountain States, 204 

Juniper, alligator-bark, 190 

one-seeded, 190 

Juniperus, cone of, 26* 

Juniperus in the Rocky Mountain States. 


Juniperus in the Southwest, 190 
Juniperus pollen, 24* 

Kaffir, 58 

Hayfever Plants 


General Index 

Kansas, 209 

Kentucky, 174 

Kentucky bluegrass, 41, 42* 

Key West, Florida, 187 

Knot grass, 44 

Kochia, 102, 192, 206 

Koeleria, 48 

Koeler's grass, 48 

Krameriaceae, 111 

Lacinaria, 151 

Lactophenol, 9 

Lactuca, 163 

Lambsquarters, 103, 176 

Lambsquarters in the Southwest, 191 

Larch pollen, 24* 

Larijf pollen, 24* 

Lawson cypress, 28, 200 

Leguminosae, 111 

Lenscale, 108 

Lettuce, 163 

Leuciva, 132 

Leverwood, 73 

Liatris, 151 

Liboccdrus, 25 

Liguli florae, 163 

Ligustrum, 121, 122, 179 

Lilac, 121 

Lilium seedling, 30* 

Linden, 116 

Linden family, 116 

Liquidambar pollen, 95* 

Lithocarpus, 75 

Locust, 115 

Lolium, 45 

Long Island, Great South Beach on, 169 

Louisiana, 178, 183 

Low ragweed, 147, 192 

Low-spear grass, 41* 

Liini and VARESCHI method of catching 

pollen, 9 
Lupulus, 92 
Luzula, 60 

Machias, Maine, 169 

Madura, 90, 91, 95*, 170 

Maidenhair tree, 20 

Maine, 169 

Maize, 58 

Mangel, 101 

Maple, 116, 166, 172, 173, 176 

Maple family, 116 

Maple in the North Pacific States, 199 

Maple in the Rocky Mountain States, 206 

Maple pollen, 111* 

Maple, ash-leaved, 120 

black, 119 

cut-leaved, 120 

hard, 119 

Norway, 117 

H Oregon, 199 

red, 118* 

rock, 119 

scarlet, 118 

silver, 119 

soft, 118 

sugar, 119* 

swamp, 118 

sweet, 119 

sycamore, 117 

white, 118 

Marigold, 150 
Marigold, pot, 150 
Marram grass, 51 

Marshelder, 132, 133*, 168, 171, 181, 201 
Marshelder in the Southwest, 193 
Marshelder, common, 133 

rough, 134*, 176 

i small-flowered, 135 
Marsh grass, 168 
Marsh spike grass, 43 
Maryland, 169, 170 
Mayweed tribe, 151 
Meadow foxtail, 48, 167 
Meadow grass, rough-stalked, 42 
Meadow sweet, 109 
Medicago, 115 

Mclilotus, 115 

Mesquite, 111, 113, 190 

Mesquite pollen, 112* 

Mexican screw bean, 114 

Mexican tea, 103, 104*, 168 

Miami, Florida, 187 

Miami Beach, Florida, 187 

Michigan, 174 

Middle Atlantic States, 169 

Middle Atlantic States, hay fever plants of, 


Midwinter hayfever, 178 
Milkweed flower, 4* 
Mimosa, 111 
Mimosaceae, 111 
Mimosa family, 111 
Mimosa tree, 114 
Minnesota, 209 
Mississippi, 178 
Missouri, eastern, 174 
Missouri, southern, 178 
Mock orange, 91 
Momisia, 87 
Manilla, 186 
Monocotyledons, 30*, 32 
Monocotyledons, leaves of, 30* 
Monoecious, 2 
Monolepis, 101 
Montana, 204 

Montauk Point, Long Island, 169 
Montgomery, Alabama, 183 

Roger P. Wodehouse 


Hayfever Plants 

Moraceae, 90 

Morus, 90 

Morus pollen, 95* 

Mountain ash, 109, 124 

Mountain cedar, 27, 178 

Mucoralcs, 187 

Muehlenbeckia, 92 

Mugwort, 153, 173 

Mugworts in the North Pacific States, 201 

Mugworts in the Southern States, 181 

Mugwort, California, 156, 207 

Canadian, 160 

common, 155 

dark-leaved, 156 

saw-leaved, 157 

seashore, 160 

western, 157 

Mulberry, 90, 170 
Mulberry family, 90 
Mulberry pollen, 95* 
Mulberry, red, 90 
paper, 90 

white, 90 

Mutisia tribe, 162 
Mutisieae, 162 
Myrica, 86 
Myricaceae, 86 
Myrica pollen, 95* 

Nassauvinae, 163 

Natal grass, 55, 179 

Nebraska, 209 

Negundo, 120 

Nettle tree, 87, 89 

Nevada, 197 

New England States, 164 

New Jersey, 164 

New Mexico, 188 

New York, 164 

Nogal, 84 

North Carolina, 172 

North-Central States, 174 

North-Central States, hayfever plants of, 


North Dakota, 209 
Northeastern States, 164 
Northeastern States, floras of the, 16 
Northeastern States, hayfever plants of 

the, 166 

North Pacific States, 197 
North Pacific States, hayfever plants of 

the, 198 
Nothofagus, 75 
Nothoholcus, 48 
Nova Scotia, 169 
Nutgrass, 60 
Nutrush, 60 

Oak, 75, 76*, 167, 169, 173, 176, 179 
Oak in the North Pacific States, 200 

Oak in the Southwest, 190 
Oak leaves, 78* 
Oak pollen, 85* 
Oak, bear, 80 
bellota, 190 

black, 77, 80 

black-jack, 79 

blue, 200 

California black, 200 

California scrub, 80 

chestnut, 77, 79 

coast live, 80, 200 

cork, 77 

dwarf live, 80 

eastern, 80 

Engelman's, 79 

English, 77 

evergreen, 79 

- Garry's, 79 
gray, 77 

highland live, 80 

interior live, 80, 200 

iron, 79 

live, 77, 80 

maul, 80 

mesa, 79 

Oregon, 79, 200 

pin, 78 

post, 79 

red, 77, 78 

scarlet, 77 

scrub, 77, 80, 200 

scrub live, 80 

Spanish, 77, 78 

swamp, 78 

swamp white, 80 

. tan-bark, 75 

Texas live, 80 

twin live, 80 

valley, 200 

white, 76*, 77, 79 

willow, 77, 79 

Oat, 47 

Obione, 105 

Ohio, 174 

Oklahoma, 178, 182 

Oklahoma, flora of, 17 

Old man, California, 154 

Olea, 121 

Olcaccae, 121 

Olea pollen, 112* 

Olive, 121 

Olive family, 121 

Olive pollen grain, 112* 

Ontario, southern, 174 

Open dish method of catching pollen, 9 

Opopanax, 113 

Orach, 104 

Orach, garden, 105 

Hayfever Plants 


General Index 

Orchard grass, 43*, 167, 170, 174, 179 

Oregon, 197 

Osage orange, 91, 170 

Osage orange pollen, 95* 

Ostrya, 73*, 211 

Oxytenia, 132, 135 

Oyster plant, 163 

Pacific Coast, floras of the, 17 

Palms, the, 34 

Panama City, Florida, 187 

Panic cac, 55 

Paper mulberry, 170, 182 

Paper mulberry pollen, 95* 

Papyrins, 90 

Parthcnium, 132 

Paspalum, 56, 206 

Pass Christian, Mississippi, 187 

Pasture sage, 158 

Peach, 109, 110 

Pea family, 114 

Pear, 109 

Pecan, 84, 173, 179 

Pcnicillium, 186, 187 

Pennsylvania, 164 

Pepper tree, 201 

Pcrezia, 162 

Perianth, 2 

Persicaria, 92 

Phalaridcac, 55 

Phalaris, 55 

PMcum, 49*, 179 

Phlcum pollen grain, 35* 

Picea, 23 

Picca pollen, 24* 

Pickleweed, 101, 200 

Picrothamnus, 161 

Pigeon grass, 56 

Pigeon plum, 92 

Pigweed, 96, 98*, 168 

Pigweed family, 95 

Pigweed in the Rocky Mountain States, 


Pigweed in the Southwest, 191 
Pigweed pollen, 95* 
Pigweed, redroot, 97 
winged, 101 
Pikes Peak, 206 
Pine, 22 

Pine, cones of, 22* 
Pinus, 22 
Pinus pollen, 24* 
Piqueria, 151 
Pistils, 1 

Plains and prairies, 209 
Plains and prairies, hayfever plants of the, 


Planer a, 87 
Plane tree, 110 

Plane tree family, 110 
Plane tree, London, 111 

Oriental, 111 

Plantaginaceae, 125 
Plantago, 125, 126* 
Plantago pollen, 112* 
Plantain, 125 
Plantain family, 125 
Plantain pollen, 112* 
Plantain, common, 127 

English, 125, 126*, 167, 171 

greater, 127 

Rugel's, 127 

Platanaceae, 110, 125 
Platanus, 110, 176 
Platanus pollen, 112* 
Plum, 109 

Poa, 40, 41*, 42* 

Poa in the Southwest, 191 

Poison grass, 45 

Pollen from herbarium specimens, 15 

Pollen slides, preparation of, 14 

Polygonaceae, 92 

Pond grass, 44 

Popinack, 113 

Poplar, 61, 64, 167, 170, 173 

Poplar in the Southwest, 189 

Poplar leaves, 65* 

Poplar pollen, 69* 

Poplar, balsam, 66 

black, 64 

Carolina, 66, 167 

i Lombardy, 64 

necklace, 66 

silver, 64 

western, 66 

white, 64 

Pofinlus, 61, 64, 173, 178 

Populus in the North Pacific States, 200 

Populus in the Rocky Mountain States, 205 

Populus in the Southwest, 189 

Portland, Maine, 169 

Port Orford Cedar, 28 

Poverty oatgrass, 48 

Poverty weed, 101, 135, 193 

Prairie June grass, 48 

Prairie ragweed, 132, 135, 136*, 193 

Prairie ragweed in the North Central 

States, 175 
Prairie ragweed in the Southern States, 


Prairie ragweed pollen, 129* 
Prairie sage, 156-158 
Prairie wormwood, 156 f 

Prince's feather, 92, 96 
Privet, 121, 122* 
Privet, California, 122 

common, 123 

Roger P. Wodehouse 


Hayfever Plants 

glossy, 123 

southern, 123 

Prosopis, 113, 190 
Prunus, 110 
PsyUium, 125 
Pullularia, 187 
Purple osier, 166 
Pyrethrum, 152 
Pyrus, 110 

Quackgrass, 44, 167 

Quailbrush, 108 

Quassia family, 115 

Quercus, 75, 76*, 167, 169, 173, 179 

Quercus in the North Pacific States, 200 

Quercus in the Southwest, 190 

Quercus leaves, 78* 

Quercus pollen, 85* 

Quichens, 44 

Quitchgrass, 44 

Quiver leaf, 66 

Rabbit bush, 146, 192 

Ragweed, 137 

Ragweed flower heads, 137* 

Ragweed in North-Central States, 174 

Ragweed in the Southern States, 181 

Ragweed seedling, 31* 

Ragweed seeds, 138* 

Ragweed tribe, 132 

Ragweed, common, 139 

dwarf, 195 

giant, 142 

seashore, 144 

short, 139, 140* 

short, in Middle Atlantic States, 171 

short, in North-Central States, 175 

short, in Northeastern States, 167 

short, pollen grain, 129* 

Southern, 143*, 175 

Southern, staminate head, 143* 

tall, 141*, 142 

tall, in the Middle Atlantic States, 


tall, in North-Central States, 175 

Texas great, 142 

Tiajuana, 144, 195 

western, 144, 192 

western giant, 142 

western, in the North Pacific States, 

western, in North-Central States, 


Randall grass, 39 
Rangeley Lake, Maine, 169 
Ranunculus acris, 1* 
Raspberry, 109 
Raygrass, 45 
Raygrass, red, 45 

Receptacle, 1* 

Red cedar pollen, 24* 

Red dare, 45 

Red darnel, 45 

Red orach, 105 

Redsage, 103 

Redtop, 50*, 51, 167, 174 

Regional surveys, 7, 164 

REMPE, method of catching pollen, 9 

Restricted groups, monographs of, 19 

Retinospora, 28 

Rhubarb, 92 

Rhubarb, wild, 94 

Ripgut grass, 38 

Robinia, 115 

Rocky Mountain region, floras of the, 17 

Rocky Mountain States, 204 

Rocky Mountain States, hayfever plants 

of the, 205 
Romerillo, 196 
Rosa, 110 
Rosaceae, 109 
Rosa pollen, 112* 
Rose, 109 
Rose cold, 110 
Rose family, 109 
Rose pollen, 112* 
Rulac, 120 

Rumex, 92, 93*, 94*, 173, 201, 212 
Rumex pollen, 95* 
Rushes, true, 60 
Rush pollen grain, 69* 
Rush, wood, 60 

Russian thistle, 102, 173, 174, 192 
Russian thistle in the North Pacfic States, 


Russian thistle in the Southern States, 181 
Russian thistle pollen, 95* 
Rye, 46 
Ryegrass, 45 
Ryegrass, Italian, 45 
perennial, 46* 

Sage, gray, 207 
green, 207 

pasture, 207 

Sagebrush, 153 

Sagebrush in the North Pacific States, 


Sagebrush pollen, 129* 
Sagebrush, California, 154 

coast, 154-156* 

common, 161, 193 

dwarf, 158 

flat, 158 

green, 159 

mountain, 161 

sand, 160 

spiny, 161 

Hayfever Plants 


General Index 

Sage wort, annual, 158 

biennial, 157 

common, 155, 158 

dragon, 207 

field, 159, 160* 

smooth, 159 

St. Augustine grass, 56 

Salicaceae, 61 

Salicornia, 102, 200 

Salix, 61, 62, 166 

Salix flowers, 63* 

Salix in the North Pacific States, 200 

Salsify, 163 

Salsify, black, 163 

Salsola, 102, 192 

Salsola in the North Pacific States, 200 

Salsola in the Southern States, 181 

Salsola pollen, 95* 

Saltbush, 104, 108, 192, 200, 207 

Saltbush, annual, 107* 

Australian, 106 

" four-winged, 108 

spiny, 109 

Saltgrass, 43, 191 

Salt Lake City, Utah, 206 

Saltmeadow cordgrass, 54 

Saltwort, 102 

Samphire, 102 

Sand bur, 147 

Sarcobatus, 102 

Sarcobatus pollen, 95* 

Savannah Beach, Georgia, 187 

Savin, 26 

Schinus, 201 

Scirpus, 59 

Scolymus, 163 

S cor sonera, 163 

Screw-pod mesquite, 114 

Scrub elm, 182 

Scutch grass, 51 

Seablite, 102 

Sea grape, 92 

Sea marram, 51 

Sea-mat weed, 51 

Sea-sand reed, 51 

Secale, 46 

Secale pollen, 35* 

Sedge, 59 

Sedge pollen, 35* 

Sedge, tussock, 59 

Seepweed, 102 

Senecio, 162 

Senecioneae, 162 

Sensitive plant, 111 

Sepal, 1* 

September elm, 182 

Shadscale, 108, 109, 192 

Shallu, 58 

Shear grass, 44 

Sheep sorrel, 92 

Shelly grass, 44 

Short grass, 53, 56 

Silk-tassel bush, 203 

Silver scale, 106 

Silvery orach, 106 

Simarubaceae, 115 

Slender ragweed, 145, 146*, 192, 196, 207 

Slough grass, 44 

Sneezeweed, 150 

Sneezeweed tribe, 150 

Sod houses, 54 

Solidago, 150, 168 

Solidago pollen, 129* 

Sonora bursage, 147 

Sorbus, 109 

Sorghastrum, 182 

Sorgho, 58 

Sorghum, 57*, 58, 190 

South Carolina, 172 

South Dakota, 209 

Southeastern United States, floras of the, 

Southern California, hayfever plants of, 


Southern States, 178 

Southern States, hayfever plants of, 180 
Southernwood, 154 
Southwest, 188 
Southwest, floras of the, 17 
Southwest, hayfever plants of the, 188 
Spanish oyster plant, 163 
Spartina, 168 
Spike-rushes, 59 
Spinacea, 101 
Spinach, 101 
Spiraea, 109, 110 
Spirostachys, 101 
Spondilocladium, 187 
Spruce, 23 
Spruce pollen, 24* 
Squirrel tail, 45 
Stamens, 1* 
Steeple bwsh, 109, 110 
Stenotaphrum, 56 
Stevia, 151 
Stigma, 2 
Stoke's aster, 151 
Stokesia, 151 
Strawberry, 109 
Straw flower, 150 
Stroil, 44 

Strombocarpus, 114 
Style, 2 

Sudan grass, 58 
Sueda, 102 
Sugar beet, 101 
Sugarberry, 89 
Sulphur showers, 5 

Roger P. Wodehouse 


Hayfever Plants 

Summer cypress, 102 

Sunflower, 131, 132, 176, 193, 201 

Sunflower family, 127 

Sunflower pollen, 129* 

Sunflower tribe, 131 

Sweet clover, 115 

Sweet fern, 86 

Sweet gale, 86 

Sweet gale pollen, 95* 

Sweet gum, 167 

Sweet gum pollen, 95* 

Sweet vernalgrass, 54*, 55, 167 

Swiss chard, 101 

Sycamore, 110, 170, 176 

Sycamore family, 110 

Sycamore pollen, 112* 

Sycamore, western, 111 

Sydney golden wattles, 113 

Synthcrisma, 56 

Syringa, 121 

Tacamahac, 66, 167 
Tagctes, 150 
Tallow shrub, 86 
Tanacetum, 152* 
Tansy, 152* 
Taraxacum, 163 
Taraxacum pollen, 129* 
Tarragon, 159 
Tennessee, 178, 183 
Texas, eastern, 178, 184 
Texas, western, 188 
Thistle, 162 
Thistle tribe, 162 
Thistle, bull, 162 

Canada, 162 

globe, 162 

star, 162 

Thuja, 25 
Tidestromia, 100 
TiVi'o, 116 
Tiliaceae, 116 

Timothy, 49* 167, 171, 174, 179 
Tornillo, 114 
Toxylon, 91 
Tracaulon, 92 
Tragopogon, 163 
Tree-of -heaven, 115 
Tree-of-heaven pollen, 129* 
Trees, botany of the, 18 
Trembling aspen, 167 
Trichoderma, 186 
Tricholaena, 55, 179 
Trijolium, 115 
Tripsaceac, 58 
Triticum, 44 
Triumjetta, 116 
Trixis, 162 
Tsuga, 25 

Tsuga, cone of, 22* 
Tsuga pollen, 24* 
Tumbleweed, 102, 191 
Twitchgrass, 44 
Twitchgrass, black, 40 
Typha, 32, 33* 
Typhaccac, 32 
Typha pollen, 35* 

Ulmaceae, 86 

Ulmus, 87*, 88*, 166, 173 

Ulmus in the Southern States, 182 

Ulmus pollen, 85* 

Utah, 204 

Vaseline, method of catching pollen, 9 

Vasey grass, 57 

Velvet grass, 47*, 48 

Vernonia, 151 

Vernonieae, 151 

Virginia, 172 

Virginias and Carolinas, 172 

Virginias and Carolinas, hayfever plants 

of the, 172 
Vulgaris group (Artemisia}, 155 

Wahoo, 88 

Walnut, 82 

Walnut family, 81 

Walnut in the North Pacific States, 199 

Walnut pollen, 85* 

Walnut, Arizona, 84 

black, 82*, 83 

English, 82 

Persian, 82 

Washington, 197 
Water ash, 120 
Water elm, 87, 88 
Water grass, 56 
Waterhemp, 99 
Water oats, 55 
Waxberry, 86 
Wax myrtle, 86 

Wax myrtle, California, 86 

Way bent grass, 45 

WELLS air centrifuge, 10, 11* 

Western June grass, 48 

Western waterhemp, 99*, 100, 175, 179, 

191, 207 

West Virginia, 172 
Wheat, 44 
Wheatgrass, 44, 206 
Wheatgrass, western, 44 
White Mountains, New Hampshire, 169 
White pine, cones of, 22* 
Whitetop, 51 
Whitewood, 116 
Wickens, 44 
Wild barley, 45 

Hayfever Plants 


General Index 

Wild oat, 47 

Wild oat, slender, 47 

Wild oatgrass, 48, 167 

Wildrice, 55 

Willow, 61, 62, 166, 176 

Willow flowers, 4, 63* 

Willow in the North Pacific States, 200 

Willow leaves, 65* 

Willow pollen grains, 69* 

Willow, arroyo, 200 

brittle, 62 

* crack, 62, 65* 

dune, 200 

purple osier, 62 

pussy, 62 

red, 200 

silver, 62 

Sitka, 200 

snap, 62 

swamp, 62 

weeping, 63 

white, 63 

Wingscale, 108, 192 
Wingscale pollen, 95* 
Winter fat, 101 
Wintergrass, 45 

Wiregrass, 41, 51 

Wisconsin, 174 

Witchgrass, 44 

Woollyfoot, 53 

Wormwood, 153 

Wormwoods in the Southern States, 181 

Wormwood, annual, 158 

biennial, 157 

common, 158 

linear-leaved, 159 

T saw-leaved, 157 

silvery, 161, 193, 207 

tall, 159 

Wyoming, 204 

Xanthium, 133, 147, 148* 

Xanthium in the Plains and Prairies, 213 

Xanthium in the Southern States, 181 

Xanthium pollen, 129* 

X-hayfever, 185 

Yarrow, 152 

Zea, 58 
Zizanea, 55 
Zisaneae, 55 


Chronica Botanica, an international collection of studies in the method, 
philosophy, and history of biology and agriculture, aims at the promo- 
tion of (1) international relations in the plant sciences, (2) studies in 
the history, method, and philosophy of biology and agriculture, (3) a 
better understanding between specialists in various branches and their 
relations with the outside world. 

Chronica Botanica is published bimonthly and contains about 600 pages of memoirs, 
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CHRONICA BOTANICA was founded, *nd it edited by FRAN a and J. G. VERDOORN, in cooperation with the following advisory 
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C. G. G. J. VAN STEIKH, N. E. SVBDBLIUI, Acad. N. I. VAVILOV, F. W. WEMT, Assistant Editors: V. C. Asuous, 
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W. B. TURRILL, S. A. WAKSMAN, JOB. WESTERDIJK, C. T. WHITE. A complete list of all our contributors and corre- 
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Europe to postmaster-amateur botanists in S. America, from foresters in Russia to agricultural chemists in Australia, from 
phytopathologists in China to young botany students in Sweden. 

> An International Plant Science Addressbook and Rt filter, to b published as soon as possible after the War, in parts in 
CHRONICA BOTAHICA, is in preparation. This will include a fifth edition of our World List of Plant Science Institutions 
and Societies and, after revision, much of the material submitted for the Int. Addressbook which we were preparing in the 
unfortunate summer of 1939 (considerable parts of this have stilt been published in spite of the war in CHRONICA 6, nos. 12 
and 13 and CHRONICA 7, no. 3). 

>> In forthcoming volumes of the CHRONICA we will publish an extensive, critical, biographical dictionary of plant scientists 
of all times. A detailed note about this Index Botanicorum, which is being prepared with the assistance of the Aronld Arbo- 
retum of Harvard University, has been published in the Autumn Number of CHRONICA BOTANICA for 1944. Reprints of this 
article (with detailed notes for contributors) are available upon request. 

. . . more valuable to the botanical world under present conditions than even in normal times (NATURB). 

A remarkable achievement of editorial effort and co-operation ... it covers a field not hitherto pre-empted, 
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Die Botanik kann sich eines Organs riihmen, das bisher keine andere Wissenschaft kennt und das letzten Endes 
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den Arbeitsgegenstand verbundenen internationalen Gemeinschaft (ZEITSCHRIPT FUR BOTANIK). 

The first three volumes of CHRONICA BOTANICA (1935/37) were published as annual records and reviews of current research, 
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than previously dealing with the basic humaniora of the plant sciences: history, methodology and philosophy. Much space, 
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Autumn 1944 Catalogue 


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Hampshire Forestry Dept.). The first modern book 
dealing exclusively with tree seed in English. With a 
polyglot glossary of tree seed terms. A New Serifs of 
PI. Sci. Books, Vol. 8 (1942); Sup. roy. oct., buckram. 
240 pp., 28 illustr $4.75 

Contents: Structure and development. Seed production. The 
importance of seed source or provenance. Seed collection. 
Extraction. Cleaning and treatment. Storage and longevity. 
Insects, diseases and other enemies. Germination. Internal 
and eiternal factors affecting germination. Chemical aspects. 
Seed stimulation. Different kinds of tests. Purity analysis. 
Determination of origin. Testing viability without germina- 
tion. Testing of germination. Seed testing stations and 
certification. Research. Glossary. Indices. 

The material presented is critically examined, well documented, 
and there are fairly extensive lists of references to literature. 
Much of the discussion on harvesting, storage, and germination 
pertains with equal validity to many types of plants, so that 
the book has a wide field of interest and usefulness beyond the 
more immediate limits of species of trees (KRAUS in EOT. 

The work will be indispensable to research workers in the field of 
tree seed and very useful to practical foresters and members of 
the seed trade. It is not a handbook of tree seed, giving cut 
and dried information about individual species, but a reference 
book and a guide, not only to existing knowledge but also to 
the directions in which that knowledge should be extended in 
the future (THOMSON in NATURE). 

by F. C. Bawden (Rothamsted Experimental Station). 
Second entirely revised and modernized edition with 
many new illustrations. No chapter remains unchanged, 
and more than half have been completely rewritten. 
Recent advances in all branches of the subject are de- 
scribed and correlated. Techniques new to botanists 
are discussed, special attention being given to work on 
the chemical, physico-chemical and serological properties 
of purified virus preparations. Modern concepts on tho 
nature, origin, size and multiplication of viruses are 
critically reviewed. A New Series of PI. Sci. Bks., 
Vol. 13 (1943); Sup. roy. oct., buckram, 294 pp., 48 
illustr $475 

Contents: Symptomatology. Transmission. Relationships be- 
tween viruses and insect vectors. Virus strains, mutation, and 
acquired immunity. Serological reactions. Methods of purifi- 
cation. Properties of purified virus preparations. Optical 
properties of purified virus preparations. Inactivation of 
viruses. The sizes of virus particles. Physiology of virus- 
diseased plants. The classification of viruses. Control. Origin 
and multiplication of viruses. 

In recent years students of plant viruses have been joined by 
workers in subjects which at first sight seem to have little 
connection with plant pathology. Biochemists, physical chem- 
ists, serologists, statisticians and X-ray specialists have all 
taken a hand in the game and the ordinary biologist finds him- 
self somewhat bewildered by these specialists each talking a 
jargon of his own. One welcomes therefore the present volume 
which gives a lucid explanation of much of this unfamiliar 
technique . . . written in an interesting and readable style and 
the subject is presented in a coherent and consecutive manner 
and is not a mere statement of unrelated facts (K. M. SMITH 
in J. PATH. BACT.). 

This second edition is a useful and welcome compilation. 
Since the research on plant viruses has contributed so much 
to an understanding of their fundamental nature, this book 
is valuable to the animal as well as lo the plant biologist. It 
ii a fine tribute to British appreciation of fundamental science 
that this excellent work has been continued while bombs 
were falling (Ricn i* Box. GAZETTE). 

CHEMISTRY by C. A. Browne (U. S. Dept. of 
Agriculture). A History of Developments in the Ap- 
plication of Chemistry to the Theory and Practice of 
Agriculture from the Time of DEMOCRITUS to the Period 
of LIEBIG. Chronica Botanica, Vol. 8, No. 1 (1944); 
Sup. roy. oct., 290 pp., 1 plate, 32 illustr $5.00 

Contents: Agricultural chemistry in ancient times. Agricultural 
chemistry in the alchemical and iatrochfhical periods. Agri- 
cultural chemistry in the time of the early Royal Society. Agri- 
cultural chemistry in the early phlogiston period. Agricultural 
chemistry in the late phlogiston period. Agricultural chemistry 
during the chemical revolution. Agricultural chemistry at the 
beginning of the modern period. 

This is a history-of-science reference book which gives a chrono- 
logical account of attempts to apply chemical principles to the 
interpretation of the phenomena of plant and animal life in 
some of their relations to agriculture. After an introduction 
defining the scope and aims of agricultural chemistry the 
development of this science is traced in seven chapters begin- 
ning with the ancient Greek and Roman era and then con- 
tinuing through the alchemical and iatrochemical periods, the 
time of the early Royal Society, the phlogistic period and the 
chemical revolution, to the beginning of the modern period in 
the mid-nineteenth century. Brief accounts are given of the 
lives, researches, and publications of fifty different investigators 
with special stress upon ^the influences they exercised on sub- 
sequent developments. Thirty-two illustrations, from classic 
publications, of apparatus and processes, of title pages and 
specimens of text and of historic tabulations, assist the reader 
in following the explanations of the different chapters. Trans- 
lations are given of pertinent passages and each biographical 
sketch is followed with a list of references to original source 
material. A subject index and n author index facilitate the 
location of special topics. Following the indices is an adden- 
dum giving references to later source material for the guidance 
of those who desire to study more recent developments during 
the past century. 


(U. S. Dept. of Agriculture). A scholarly essay, by 
the Nestor of American Agricultural Chemists, on 
THOMAS JEFFERSON'S position in the world of science, 
his "Notes on the State of Virginia", his scientific 
services to the new republic of the United States, his 
agricultural and educational work, and some of the 
eminent contemporaries who knew JEFFERSON personally 
and exchanged with him letters that throw much light , 
on the scientific movements of the time. Chronica 
Botanica, Vol. 8, No. 3 (1944); Sup. roy. oct., 64 pp., 
illustrated with 17 contemporary drawings, maps, and 
facsimiles $1.25 

toward politics and though the trend of events caused his 
career to fall in the latter field he strove as resolutely to create 
a democracy of science as he did to establish a democracy of 
government. The publication is timely in view of the recent 
commemorations of the bicentenary of JEFFEKSON'S birth. 

liam C. DarraK (Harvard U.). A New Series of PI. 
Sci. Bks., Vol. 3 (1939); Roy. oct., 239 pp., 7 pi.; out 
of print, a new edition is in preparation for publication 
after the war. 

Eine wertvolle iibersichtliche Dantellung unserei heutigen palao- 
botanischen Wissens ... Die Gliederung, sowohl hinsichtlich 
der Pflanzenformen als auch der Pflanzengesellschaften in den 
cinzelnen geologischen Zeitepochen zeigt von universeller Be- 
herrschung del Forschungsgebietes (HorUAHN in 0rr. 
EOT. Z.). 

This book was written for the unspecialized botanical reader. It 
is in no way, however, a popularized account ... the author's 
enthusiasm is so evident that it may go a long way to inspire 
keenness (HARRIS in NATURE). 

Ghronica Botanica Go. 

Catalogue of Publications 

SIS by G. Brdtman (Vasteris, Sweden). Foreword by 
Roger P. Wodehouse, author of Tollen Grains'. The 
first and only comprehensive reference work on the 
methodology and applications of pollen analysis. A 
New Series of PI. Sci. Bks., Vol. 12 (1943); Sup. roy. 
oct., buckram, 239 pp., 46 plates and illustr $5.00 

from the contents: Historical. Chemistry of Peat. Pollen 
Preparations. Preparation of Fossil Pollen-Bearing Material. 
Pollen and Spore Morphology. Graphic Presentation. Cor- 
relation. Output and Dissemination of Pollen. Surface Sam- 
ples. Pollen Flora of Peat Samples. Investigations in dif- 
ferent Countries. Tertiary Deposits. Honey and Drugs. 

An account of the principles and methods used in research on 
pollen, especially fossil pollen. The author has brought 
together and evaluated all previous work and greatly extended 
it through his own researches. A large part of the book is 
devoted to morphology of the pollen grains of angiosperms and 
gymnosperms, and of the spores of ferns, stressing the means 
of their identification in the fossil form. This is greatly 
facilitated by several hundred original drawings from both 
fossil and living materials. The author shows the practical 
application of pollen identification in palaeoclimatology, archae- 
ology, forestry and phytogeography and other fields. His 
studies of pollen production and dissemination together with 
studies of modern pollen deposits point the way to a very 
realistic reconstruction of the past through studies of ancient 
pollen deposits. 

Deeply buried in ancient bogs are the records of the climates 
that prevailed during the years of their slow filling up. For the 
climates determined the nature of the forests in the vicinity, 
and the forests shed pollen on the mud and shallow water, 
year after year; so that now a properly trained botanist can 
accurately describe long-vanished forests by peering through 
his microscope. This branch of paleoecology looks easy but 
isn't: how to master its difficulties and avoid its pitfalls can 
be learned from 'An Introduction to Pollen Analysis' by 
G. F ; RDTMAN, Swedish master of this tedious but rewarding 

AND SOUTH AMERICA by Margaret Fulford 

(Univ. of Cincinnati). A critical monograph of one 
of the most interesting genera of liverworts, the first 
complete modern revision of the neotropical species of a 
large and difficult genus of hepaticae, since STEPHANI 
produced his confusing Species Hepaticarum. Ann. 
Crypt, et Phytop., Vol. 3; Roy. oct., ca. 240 pp., 59 
plates, in press $5.00 

kv ROOT DISEASE FUNGI by S. D. Garrett 

(Rothamsted Experimental Station). The first book 
dealing exclusively with this important group of fungi. 
Principles of root disease control are fully expounded 
for the benefit of all practising plant pathologists. Con- 
trol measures are classified separately for field, planta- 
tion and glasshouse crops. A special feature is the full 
treatment of root disease control in tropical and sub- 
tropical crops, but no important root disease of any 
crop has been omitted. Of particular interest to soil 
microbiologists will be the chapters on biology and evolu- 
tion of the root-infecting fungi. Ann. Crypt, ft Phyt., 
Vol. 1; Roy. oct., cloth, ca. 175 pp., 10 illustr., in press, 
ready autumn 1944 $4.50 

Contents.' Parasitic specialisation in the root-infecting fungi. 
Parasitic activity. Influence of soil temperature. Influence 
of soil moisture content, texture and reaction. Influence of 
soil organic content and concentration of plant nutrients. 
Saprophytic activity of the root-infecting fungi. Dormancy. 
Control in field crops: crop rotation, plant sanitation, disease 
control under the growing crop. Control of root disease in 
plantation crops: on virgin areas; in mature plantations and on 
replanted areas; special problems; glasshouse crops. 

kv WOOD PULP by Julius Grant, Author of 'Books 
and" Documents', etc. A concise treatise of the origin, 
manufacture, testing, uses, and economic importance of 

wood pulp. A Nfw Series of PI. Sci. Bks., Vol. 2 
(1938); Roy. oct., 209 pp.; out of print. It is planned 
to deal again with the subject matter of this book 
in a forthcoming volume on wood chemistry and related 

by Alexandra Guilliermond (Sorbonne), authorized 
translation from the unpublished manuscript by 
Lenette Rogers Atkinson. Foreword by William 
Seifriz. A critical review of our present knowledge 
of the cytoplasm and its morphological constituents by 
the eminent French cytologist. A New Series of PL 
Sci. Bks., Vol. 6 (1941); Sup. roy. oct., buckram, 247 
pp., 152 illustr $4.75 

Contents: General Facts on the Structure of the Plant Cell, its 
Cytoplasm and Morphological Constituents. The Physical 
Properties and General Characteristics of the Cytoplasm. Chem- 
ical Constituents. Physico-Chemical Constituents of the 
Cytoplasm. The Plastids. The Chondriome. The Relation- 
ship between Chondriosomes and Plastids. Duality of the 
Chondriome. Hypotheses Relative to the Role of Chondrio- 
somes and Plastids. The Vacuoles. Vital Staining of the 
Vacuoles. Development of the Vacuolar System. Origin and 
Significance of the Vacuoles. The Role of the Vacuolar System 
and Hypotheses concerning it. Golgi Apparatus, Canaliculi 
of Holmgren and other Cytoplasmic Formations. Lipide 
Granules, Microsomes and other Metabolic Products. Cyto- 
plasmic Alterations. 

The present volume is the first addition, printed in America, 
to the list of books which Dr. FRANS VERDOORN is editing and 
publishing under the title, A New Series of Plant Science Books. 
Mrs. ATKINSON has accomplished an excellent job of translating 
and interpreting for English readers a highly stimulating work, 
which can be recommended to botanists generally (BeAL in 

This book gives a thorough, critical and well-balanced survey 
of the various theories on cytoplasm, chondriosomes, plastids, 
vacuoles, etc., in which both the morphological and the func- 
tional (physico-chemical) point of view have been adequately 
stressed. Though the author, as one of the leading cytologists, 
has his own pronounced views, he always does justice to con- 
trary views, so that a very high degree of objectivity in the 
treatment is obtained (LUTJEHARMS in J. S. AF. BOT.). 

TION OF PLANTS by D. R. Hoagland (Univ. of 
California). This series of lectures, based on the 
Prather Lectures at Harvard University, delivered by 
the author in the spring of 1942, outlines a number of 
important problems of plant nutrition, with a very 
considerable amount of illustrative material derived 
from extensive researches at the Univ. of California. 
Scientific aspects of certain soil-plant interrelations, 
nutrient absorption and utilization, and artificial culture 
methods are primarily discussed. Trends of research in 
plant nutrition and opportunities for further exploration 
are stressed. The discussions have been prepared with 
consideration given to the broad interests of plant scien- 
tists who are not specialists in the subjects presented, 
but who wish to learn of the nature of prdblems of plant 
nutrition, especially of recent advances in this field, as 
they may have a bearing on related fields of research. 
A New Series of Pi Sci. Bks., Vol. 14 (1944); Roy. 
oct., buckram, 226 pp., numerous ill., tables and 
plates $4,00 

Contents: A survey of problems. Micronutrient chemical elements 
and plant growth. The absorption and accumulation of salts. 
Upward movement and distribution of inorganic solutes. The 
growth of plants in artificial media. Some biochemical prob- 
lems associated with salt absorption. Aspects of the potassium 
nutrition of plants as illustrating problems of the system, soil- 

The book is especially valuable as there does not exist a general 
account of recent advances in the subjects discussed, though 
important progress has been made in recent years, in our 

Catalogue of Publications 


Ghronica Botanica Co. 

knowledge of plant nutrition. Advances in this field ire of 
interest not only to the plant physiologist, but also to the 
general physiologist, the agronomist, horticulturist, plant 
pathologist and toil scientist. 


(Connecticut Agric. Experiment Station). An ex- 
amination of the physics and chemistry of the mechan- 
isms by which fungicides control plant diseases. Per- 
tinent data are reviewed and critically discussed in the 
light of a relatively new tool for assay; namely, dosage- 
response. An analysis is given of the problem of 
deposition, coverage and tenacity as factors in pro- 
tection. A discussion is also given of the factors in 
chemotherapy, synergism, and modes of toxic action, for 
copper and sulphur, fungicides. The book ends with a 
chapter on the new organic fungicides and phytotoxicity. 
Ann. Crypt, et Phyt., Vol. 2; Roy. oct., cloth, ca. 
240 pp., 20 illustr., in press, ready winter 1945. . . .$5.00 

Contents: Historical introduction. Some general concepts. 
Laboratory assay. Some problems of data assessment. Prin- 
ciples of chemical protection. Deposition. Coverage of single 
surfaces. Coverage of multiple surfaces. Tenacity. Chemo- 
therapy. Action of copper. Action of sulfur. Action of 
organic nitrogen compounds. Action of other organic com- 
pounds. Antagonism and synergism. Phytotoxicity. 

WORLD by Homer A. Jack, Ph. D. An extensive 
and critical study of the aims, scope and organization of 
the biological field stations of the world. A unique 
account of great practical, as well as historical interest. 
Based on the results of years of travel and world wide 
systematic enquiries. Chronica Botanica, Pol. 9, No. 
1; Sup. roy. oct., ca. 90 pp., illustrated, in press, ready 
autumn 1944 $2.50 

From the contents: Purpose of biological stations. History. 
Location. Administration. Equipment. Living Facilities. In- 
struction. Educational Philosophy. Research. Annotated 
list of biological stations, covsring the entire world, with much 
practical information, publications, references, etc. 

Lloyd. Since the appearance of CHARLES DARWIN'S 
"Insectivorous Plants" in 1875 no comprehensive treatise 
on these biologically exceedingly interesting plants has 
appeared. The gradual advance of our knowledge haa 
been summarized from time to time by DRUDE, PFEFFER, 
ED. MORREN, HOOKER, GOEBEL and LLOYD, but a fully 
documented treatment was greatly needed. The illus- 
trations are nearly all original and include numerous 
halftone plates, enabling the reader to visualize the 
forms discussed, and a large number of line drawings 
amplifying the text. A New Series of PI, Sci. Bks., 
Pol. 9 (1942); Sup. roy. oct., buckram, 352 pp., several 
hundred illustrations $6,00 

Contents: Introduction. Heliamphora. Sarracenia. Darling- 
tonia californica. Nepenthes. Cephalotus follicularis. Gen- 
lisea. Byblis. Drosophyllum lusitanicum. Pinguicula. Drosera. 
The carnivorous Fungi. Dionaea. Aldrovanda. Utricularia, 
Biovularia, and Polypompholyx. Indices. 

It is so clearly and entertainingly written that anyone with a 
modicum of botanical knowledge can enjoy it and use it as a 
guide. Professor LLOYD'S drawings and photographs are very 
clear and helpful, and the 38 plates incorporate hundreds of 
them. Production is of the high standard we have learnt to 
expect from Chronica Botanica. Altogether, a distinguished 
performance for which thanks and congratulations are due to 
both author and publisher (STEPHENS in ]. So. Ar. EOT.). 

It is, therefore, the more commendable and welcome that finally- 
LLOYD has completed this comprehensive authoritative, and 
detailed study of the carnivorous plants. Any such study 
which traces a function or an activity through the diverse 

plants possessing it is bound to have a significant influence on 
science, and this authoritative volume without doubt will 
prove to be an epoch-making one. Comprising in large part 
the author's own original work, yet with a masterly synthesis 
of all the pertinent work previously done by others, the book 
has a thoroughness and completeness that stamp it as out- 
standing. All possible aspects of th{ plants concerned < 
their taxonomy, anatomy, physiology, ecology, and relation- 
ship are considered in detail, with authoritative knowledge 
derived from the writer's 13 years of enthusiastic devotion to 
this field, devotion that involved careful absorption of an 
extensive literature in several languages, and first hand study 
of living material on this continent, in Europe, and in more 
remote localities during two journeys one to Africa, another 
to Africa and Australia supplemented by extensive corre- 
spondence, by securing the cooperation of collectors and natu- 
ralists in favorable localities, and by periods of study at 
various botanic gardens and laboratories ... the volume is a 
beautiful job of craftsmanship (QUART. REVIEW oj BIOL.). 

> TREE GROWTH by D. T. MacDougal (Carnegie 
Inst. of Washington). A presentation of the results 
of physiological and ecological studies of growth of 
pines, spruces, firs, larches, redwoods, cypresses, oaks, 
ashes, willow, poplar and other trees, beginning with the 
contributions of R. HARTIG and H. VON MOHL, and in- 
cluding the extensive observations of the author during 
the last twenty years. Inception of growth, duration of 
seasonal activity of the cambium, correlation of growth 
in roots, trunks and buds, and relation of area of leaf- 
surface to volume of wood formed, receive comprehen- 
sive treatment. A New Series of PI. Sci. Bks., Pol. 1 
(1938); Roy. oct., 240 pp., 20 illustrations; out oj 
print. Some time in the future we hope to publish a 
revised ed. or to include a treatment of the essentials of 
tree growth in a book on tree physiology. A few copies 
may still become available when we can again get in 
touch with our continental agents. 

H. Pfeiffer (Bremen). The first comprehensive re- 
view by an internationally known and appreciated 
authority. ^ New Series oj PL Sci. Bks., Pol. 4 
(1940); Roy. oct., 243 pp., 28 illustr.; out of print. A 
few copies may again become available as soon as we 
will be able to get in touch with our agents in the 
Netherlands. A second revised and enlarged edition 
will be published some years after the war. 

Experimental cytology is one of the most flourishing fields of 
research in present-day biology. The birth of the new sciences 
biophysics and biochemistry, the introduction of tissue culture, 
the inauguration of the periodical Protoplasms, and the appear- 
ance of several volumes on the physics and chemistry of 
plotoplasm, all are indications of the great activity in this new 
field of scientific endeavor. To this new field, Dr. PFEIFFER 
has contributed his book on Experimental Cytology. There are 
twenty chapters, the subjects of which range from the struc- 
ture of protoplasm, the permeability, vital staining, electro- 
physiology and the experimental control of development. The 
author's own research and world-wide relations give him 
the background necessary for a presentation of a discussion on 
cytology and genetics. 

*> A LIFE OF TRAVELS by C. S. Rafinesque 

(1836). A complete and verbatim reprint of the ex- 
tremely rare autobiography (1836) of this famous and 
eccentric naturalist. Chronica Botanica, Pol. 8, No. 2 
(1944); Sup. roy. oct., 72 pp., 5 portraits $2.50 

Contents: Life and Travels till the first departure for America. 
Travels in North America during three years. Ten years' 
residence and travels in Sicily. My shipwreck and travels 
till 1819. Seven years' residence and travels in Kentucky. 
Travels from 1825 to 1830, in Virginia, Ohio, New York, etc. 
Travels and researches 1831/33. The sources of the R. Dela- 
ware and Susquehana. Conclusion. Travels and researches 
in 1834 and 1835, sources of the Schuylkill, central Alleghanies 
of Pennsylvania, Savings Banks, etc. 

FITZPATKICC (1911) lists only 17 known copies in the libraries 
of the world. RATIKESQUE was born near Constantinople in 

Chronica Botanica Go. 

Catalogue of Publications 

1783 and died in Philadelphia, Pa., in 1840. He ii the 
author of more than 900 papers, chiefly appertaining to North 
America, covering tuch varied subjects as botany, zoology, 
medicine, history, archaeology, philology, banking, education, 
poetry, etc. Foreword by E. D. MERRILL and a critical index 
of personal names by F. W. FINN ELL, the authors of several 
recent, critical papers on RAHNBSQUE. 

SCIENCES by H. S. Reed (U. of California). A 
readable account of the growth of the plant sciences 
from early times to the present. The first 'History of 
Botany' written by an American and published in the 
U. S. A. - A New Serifs of PL Sci. Bks., Vol. 7 (1942) ; 
Sup. roy. oct, buckram, 323 pp., 37 illustr $5.00 

Contents: Introduction. Gardeners and Herbalists of Antiquity. 
The Nascent Period. The Retrogressive Period. The Renascent 
Period. The Seventeenth Century. The Eighteenth Century. 
Gardens and Other Things. Plant Geography in the Nine- 
teenth Century. Morphology. Cytology. The Water Economy 
of Plants. The Fixation of Carbon. The Assimilation of 
Nitrogen. The Fixation and Metabolism of Nitrogen. Plant 
Nutrition. Mineral Constitutents in Metabolism. History of 
Mycology. Plant Pathology. Significant Names in the HU- 
tory of Botany. 

REED'S "Short History" is more than a dry record of progress. 
Through the kind and appreciative eyes of one of America's 
best-liked botanists the kaleidoscopic change in scenes and 
actors on the stage of botanical progress becomes a vivid adven- 
ture. This book will be enjoyed not only by professional 
botanists but also by students and others. . . . This book is 
thoroughly original, in scope and treatment as well as in 
illustrations. We do not find the traditional portraits of the 
paragons of science which often are of questionable authentic- 
ity and usually are entirely non-committal as to the character 
of the subject. Instead, original illustrations of significant 
experiments, laboratories or publications are depicted, with 
delightful originality. One of the special values of the book 
is the adequate, though not undue, stress laid on the contribu- 
tions of American scientists. The reviewer was surprised to 
find how seldom he disagreed with the author, which can only 
be attributed to the care with which Dr. REID has considered 
each contribution and the sympathy with which he has treated 
each contributor. It is easier to criticize mistakes than to 
appreciate positive advances, which become incorporated in 
our general body of knowledge and which can be recognized 
as advances only after careful consideration (WEKT in SCIENCE). 

NIQUE par Auguste de Saint-Hilaire, with a bio- 
graphical sketch by Anna E. Jenkins. Chronica Bo- 
tanica, Yd. 9, No. 2; Sup. roy. oct., ca. 80 pp., illus- 
trated, in press, ready winter 1945 $2.50 

This extensive travel account, reprinted from SAINT-HILAIRE'S 
Histoire del Plantis Its plus remarquables du Brtsil tt dv 
Paraguay, is being reprinted primarily at the request of a 
number of S. American botanists. Though in the first place of 
interest to botanists (the author gives an accurate description 
of his route) it contains much of a general biological, geo- 
graphical and historical interest. 

kv PLANTS AND VITAMINS by W. H. Schopfer 

(Univ. of Berne), authorized translation from the 
author's unpublished French-Swiss manuscript by Nor- 
bert L. Noecker (U. of Notre Dame). Foreword by 
W. J. Robbins. A critical review of the vitamin 
problem, written from the viewpoint of general physi- 
ology, transecting the various fields of biology; micro- 
biology, plant and animal physiology, biochemistry, 
morphology, cytology, genetics, medicine, plant pathol- 
ogy, horticulture, and agriculture. The practical appli- 
cations of vitamin research are given special considera- 
tion. The theoretical aspects are also treated and 
should be of interest to students and teachers of 
general biology. A New Series of PI. Sci, Bks., 
Vol 11 (1943); Sup. roy. oct., buckram, 300 pp., 20 
illustr $4.75 

Contents: The Plant Cell and its Capacity for Synthesis. The 
experimental Study of Growth Factors and the Selection of 
Test Plants. Classification, Terminology, and Definition of 
Active Substances. The principal Vitamins synthesized by 
Plants. Their Action on Plants synthesizing them. The Bio- 
synthesis of Vitamins. Thiamin. Yeast and Bios. Nicotinic 
Acid, its Amide, and other Analogues. Staphylococcus aureus. 
Riboflavin, Pyridoxine, and their Analogues. The Lactic Bac- 
teria. The nitrogen fixing Bacteria. The Hemophilic Organ- 
isms and their Group of Growth Factors. Individual Factors: 
Ascorbic Acid, Cholesterol and Vitamin D, Pimelic Acid, the 
SH- Group. The Function of Growth Factors of Vitamin 
Nature. The Vitamins as Coenzymes. The Vitamins in rela- 
tion with other active Substances. General Consideration 
concerning the Presence and the loss of the Capacity for Syn- 
thesis. Vitamins in Nature. Their Role in Agronomy and 
Horticulture. Vitamin Cycles. Growth Factors and Sexuality. 
Symbiosis, Parasitism, and Vitamins. Miroorganisms as 
biological Test Objects for Vitamins. 

It is that rare thing: a complete textbook. Apparently every- 
thing relevant has been included, and the matter is right up to 
date as far as it is possible for it to be. 'Plants and Vitamins' 
gives the conspectus of a new subject the need of plants 
for vitamins. Ten years ago there was not one convincing 
example of the importance of a known and characterized 
vitamin for the growth of any plant or micro-organism, though 
possibilities had been suggested by BOTTOULEY, Miss MOCKI- 
RIDCE and others, whose interest lay chiefly in the effects of 
organic manures and soils. Our knowledge of the relation 
between plants and vitamins has come largely from the work 
of Dr. ScHorrER, who since 1933 has been Professor of Botany 
in the University of Bern. The basic experiments on the 
thiamin requirements of the fungus Phy corny cts are due to 
him; and in this book he presents the whole story. He has 
been ably aided by the translator (NicoL in SOILS AND FER- 

Few studies in biochemistry have aroused such popular interest 
as the remarkable advances made in recent years concerning the 
dependence of animals on small doses of those substances, 
produced mainly by plants, which we call the vitamins. It is 
natural that the marked heterotrophy for these substances in 
man has stimulated interest largely in the vitamin aspects 
of animal nutrition; but it has always seemed anomalous that 
the importance of vitamins to the plant which makes them, 
realized only vaguely even by many botanists, has not had 
wider publication. This gap has now been filled in this 
remarkable book, and it is well that the first major review 
should come from the hands of an expert, and indeed one who 
may be said to be the founder of the modern science of plant 
vitaminology. His book is, as it must be, of the nature of a 
preliminary report on a subject now in the full tide of develop- 
ment; but it tells, in an orderly way, of all the important 
advances made in the ten years since SCHOFFEK (1934) first 
showed the necessity for vitamins in the culture of Phycomyca, 
with sufficient bibliography to enable enthusiasts to find other 
sources of information. It is further very satisfactory that the 
author, though not hesitating to reproduce and discuss the 
structural formulae of the vitamins and to emphasize the 
vitally important, if purely chemical aspects of vitamin struc- 
ture, does not fall into the trap of making the work biochemical. 
It is a book written by a plant physiologist for plant physiol- 
ogists (P*MTOK in NATURE). 

AMERICA, edited by Frans Verdoorn. A collection 
of over a hundred accounts of the vegetation and plant 
resources (with information on agriculture, forestry, 
phytopathology, etc.) of the countries of Central and 
South America. Discussions of the aims and future of 
the plant sciences in Latin America. Several maps. 
About one third of this material has previously been 
published in CHRONICA BOTANICA and is now again 
presented after careful revision. The larger part consists 
of original contributions, not published before. All 
articles are by outstanding international authorities. 
New Series of PI. Sci. Bks., Vol. 16 (1944); Sup. roy. 
oct., buckram, ca. 400 pp., 70 illlustr., in press $6.00 

Special features are the plates, often reproduced from classical 
publications, and the extensive introductory chapters by POPEKOI 
(Problems of Tropical American Agriculture), JOHNSTON and 
SMITH (Vegetation Types), FOSBERG (Economic Botany), nd 
PKNHELL (History). There is also a special supplement by 
KRUC who reports on plant breeding in C. and S. America. 

by S. A. Wilde (Univ. of Wisconsin). The subiect 

Catalogue of Publications 

Ghronica Botanica Go. 

matter of a course given for upper class and graduate 
students in forestry, soils, botany, game management, 
and landscape architecture, embracing a wide field of 
biology and earth sciences pertinent to soils and forests. 
Deals at length with the origin and genetical properties 
of forest soils, their physics, chemistry, and biology, 
relation to forest vegetation, and importance in silvi- 
cultural management. New Series of PL Sci, Bks., 
Vol. 17; Sup. roy. oct., buckram, ca. 240 pp., illustrated, 
in press, ready autumn 1944 $4.75 

Contents: Historical and introductory. Genesis of forest toils. 
Genetic soil groups of the world: Upland soils. Genetic soil 
groups of the world: Hydromorphic and embryonic soils. Forest 
cover: its biological structure and its relation to environment. 
Physical properties of forest soils. Chemical properties of forest 
soils. Organisms of forest soils. Forest humus. Soil-forest 
types. Forest toil survey. Soils and tree planting. Ameliora- 
tion of forest soils. Thinning and selective logging in rela- 
tion to soils. Productivity of forest soil and forest manage- 
ment. Establishment of forest nurseries and control of nursery 
watering. Use of commercial fertilizers and lime in forest 
nurseries. Use of composts, liquid fertilizers, and green manure 
crops in forest nurseries. Adjustment of nursery soil fertility. 
Control of parasitic organisms in soils of forest nurseries. 

A fair balance is maintained between the theoretical foundations 
and the practical aspects of forest land utilization. All phases 
of silviculture, iriz., nursery practice, tree planting, and selective 
logging are treated from an ecological standpoint. The bibli- 
ography of several hundred references is up-to-date and inter- 
national in scope. 

by Roger P. Wodehouse (Ledcrle Laboratories). 
An authoritative botany of hayfever by the author of 
'Pollen Grains'. News Series of PI. Sci. Bks., Vol. 15 
(1945); Sup. roy. oct., buckram, 245 pp., numerous illus- 
trations and tables $4.75 

Contents: The Botany of Hayfever. The Hayfever Plants: 
Gymnosperms, Angiosperms, Monocotyledons, Dicotyledons. 
Regional Surveys. Glossary. Bibliography. 

The first and larger part of the book is devoted to pollen and 
pollination and the part that pollen plays in hayfever, as well 
as the descriptions of all of the plants known to cause hayfever, 
showing where they grow, when they flower and the character- 
istics which make them hayfever plants. The second part of 
the book is geographical, dealing with hayfever by areas 
throughout the United States, Canada and Mexico. Numerous 
illustrations of plants and their pollen grains. 

PLANT GEOGRAPHY by E. V. Wulff (Leningrad), 
authorized translation by Elisabeth Brissenden. 

Foreword by Elmer D. Merrill. An original and 
authoritative account of the general and theoretical 
problems of historical plant geography, based on the 
author's famous Russian handbook, revised and brought 
up-to-date. This American edition has been prepared 
at the request of botanists from many parts of the 
world, as there exists not a similar modern book in 
English, German or French. New Series of PL Sci. 
Bks., Vol. 10 (1943); Sup. roy. oct., 223 pp., 35 
illustr $4.75 

The last few years have furnished to the phytogeographer such 
valuable new tools and so much fresh evidence, that a phase of 
expansion of the subject clearly lies ahead. Of this our botan- 
ical students are vaguely or not at all aware, and this first 
English text to reveal the new potentialities must therefore be 
valuable and welcome. We can best convey the content of 
the book by the chapter headings: (1) historical plant 
geography: scope, relation to allied sciences, methods of inves- 
tigation; (2) history of the science; (3) areas, their centres 
and boundaries; (4) the origin of areas; (5) types of areas; 
(6) parallelism in the geographical distribution of plants and 
animals and correlation between the distribution of parasites 
and that of their host plants; (7) artificial factors in the geo- 
graphical distribution of plants; (8) natural factors in the 
geographical distribution of plants; (9) the migrations of species 
and floras and their causes; (10) historical causes for the 
present structure of areas and the composition of floras; (11) 
concept of floral elements (GODWIN in. NATURE). 

In spite of the war, and that means much more in Russia than 
in America, it has been possible to arrange for Miss BRISSENDEN 
to work in close association with Dr. WULFF in Leningrad and 
then to publish the completed manuscript in this country. 
Once more science surmounts international boundaries and the 
catastrophes of war. As Dr. MERRILL states this volume "is 
a mine of logically and authoritatively discussed information 
on the subject." The book will be of special value to plant 
geographers, because it analyzes a large amount of continental, 
especially Russian, literature not otherwise readily available 

ZoBell (Scripps Inst. of Oceanography). A mono- 
graph on hydrobacteriology with special reference to 
the distribution, characteristics, and activities of bac- 
teria and allied microorganisms in oceans, seas, and 
lakes. New Series of PL Sci. Bks., Vol. 18; Sup. roy. 
oct., buckram, ca. 250 pp., illustrated, in "press, ready 
winter 1945 $4.75 

Contents: Introduction. The marine environment. Collection 
and examination of samples at sea. Methods of enumerating 
marine bacteria. Factors influencing the distribution of bac- 
teria in the sea. Microorganisms in bottom deposits. Activi- 
ties of microorganisms in bottom deposits. Characteristics of 
marine bacteria. Aquatic yeasts and molds. Transformation 
of organic matter. The nitrogen cycle in the sea. Bacteria 
which transform sulfur compounds. The phosphorus cycle. 
Relation of marine bacteria to flora and fauna. Microorganisms 
in marine air. Sanitary aspects of marine microbiology. Eco- 
nomic importance of marine microorganisms. Microbiology of 
inland waters. Index to species of marine microorganisms. 


This new Serial consists of memoirs (each forming a 
separate volume) devoted to general and systematic 
cryptogamy and phytopathology. It continues Annales 
Bryologici of which we published 12 volumes and 4 
suppl. vols. between 1927 and 1939. Vol. 1, GARRETT, 
Root Disease Fungi and Vol. 2, HORSFALL, Fungicides 
(cf. supra) are in press. About two volumes will be 
published every year at prices ranging from $4.00 to 
$5.00, net.